How can i change the output value of an if selected?

How can i give one element of a dropdown list a value, and another element a different value? I'm trying to output the different values into a input field when selected. The following is just a visual, so you understand the problem.

<label>Dropdown-List</label>
<select class="form-control" onchange="handicap();">
<option id="c1">Example (5)</option>
<option id="c2">Example (10)</option>

<input type="text" class="form-control" id="cap">

function handicap() {

  var cap1 = document.getElementById('c1');
  var cap2 = document.getElementById('c2');

  if (cap1) {
     document.getElementById('cap').value = 5;
  }

  else {
     document.getElementById('cap').value = 10;
  }

}