Mohon bantuan mas robby untuk mengaktifkan tombol simpan

Assalam...,
Tombol simpan data masih kendala mas Robby, 
bisa tolong bantu ya? 
 
</div>
          <div style='clear:both' class="modal-footer">
            <button type="submit" name='simpanpelaksana' class="btn btn-info btn-sm">Tambahkan</button>
            <button type="button" data-dismiss="modal" aria-label="Close" class="btn btn-warning btn-sm"><span aria-hidden="true">Tutup</span></button>
          </div>
          </form>
        </div>
      </div>
</div>
 
<div class="modal fade" id="tambahbiaya" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
      <div class="modal-dialog" role="document">
        <div class="modal-content">
          <div style='margin:0px; padding-top:0px' class="modal-header">
            <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
            <h4 class="modal-title" id="myModalLabel">Tambahkan Data Biaya</h4>
          </div>
          <div class="modal-body">
              <form class="form-horizontal" action="index.php?view=kegiatan&act=edit&id=<?php echo $_GET[id]; ?>" method='POST'>
 
                <div class="form-group">
                  <label class="col-sm-3 control-label">Rincan Biaya</label>
                  <div class="col-sm-8">
                    <input type='hidden' value='<?php echo $_GET[id]; ?>' name='id'>
                    <input type="text" class="form-control" name="a">
                  </div>
                </div>
 
                <div class="form-group">
                  <label class="col-sm-3 control-label">Jumlah</label>
                  <div class="col-sm-4">
                    <input type="text" class="form-control" name="b">
                  </div>
                </div>
 
                <div class="form-group">
                  <label class="col-sm-3 control-label">Keterangan</label>
                  <div class="col-sm-8">
                    <textarea rows='5' class="form-control" name="c" required></textarea>
                  </div>
                </div>
 
          </div>
          <div style='clear:both' class="modal-footer">
            <button type="submit" name='simpanbiaya' class="btn btn-info btn-sm">Tambahkan</button>
            <button type="button" data-dismiss="modal" aria-label="Close" class="btn btn-warning btn-sm"><span aria-hidden="true">Tutup</span></button>
          </div>
          </form>
        </div>
      </div>
</div>
 
 
<div class="modal fade" id="tambahpengikut" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
      <div class="modal-dialog" role="document">
        <div class="modal-content">
          <div style='margin:0px; padding-top:0px' class="modal-header">
            <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
            <h4 class="modal-title" id="myModalLabel">Tambahkan Data Pengikut</h4>
          </div>
          <div class="modal-body">
              <form class="form-horizontal" action="index.php?view=kegiatan&act=edit&id=<?php echo $_GET[id]; ?>" method='POST'>
 
                <div class="form-group">
                  <label class="col-sm-3 control-label">Dari Karyawan</label>
                  <div class="col-sm-8">
                    <input type='hidden' value='<?php echo $_GET[id]; ?>' name='id'>
                    <input type='hidden' id='bookId' name='a'>
                    <select class="form-control" name="b">
                        <option value='0'>- Pilih -</option>
                        <?php 
                            $pelaksana = mysql_query("SELECT * FROM phpmu_karyawan ORDER BY nama_karyawan");
                            while ($p = mysql_fetch_array($pelaksana)){
                                echo "<option value='$p[id_karyawan]'> $p[nip_karyawan] - $p[nama_karyawan]</option>";
                            }
                        ?>
                    </select>
                  </div>
                </div>
 
                <div class="form-group">
                  <label class="col-sm-3 control-label">Nama Pengikut</label>
                  <div class="col-sm-8">
                    <input type="text" class="form-control" name="c" placeholder='Tulis Nama Pengikut, Jika Bukan dari Karyawan...'>
                  </div>
                </div>
 
                <div class="form-group">
                  <label class="col-sm-3 control-label">Keterangan</label>
                  <div class="col-sm-8">
                    <textarea rows='5' class="form-control" name="d"></textarea>
                  </div>
                </div>
 
          </div>
          <div style='clear:both' class="modal-footer">
            <button type="submit" name='simpanpengikut' class="btn btn-info btn-sm">Tambahkan</button>
            <button type="button" data-dismiss="modal" aria-label="Close" class="btn btn-warning btn-sm"><span aria-hidden="true">Tutup</span></button>
          </div>
          </form>
        </div>
      </div>
</div>