如何根据选中的复选框数设置按条带计费的金额按钮

<div>
  <input type="checkbox" id="stripe1" name="stripe" value="stripe1">
  <label for="stripe1">条带1</label>
</div>
<div>
  <input type="checkbox" id="stripe2" name="stripe" value="stripe2">
  <label for="stripe2">条带2</label>
</div>
<div>
  <input type="checkbox" id="stripe3" name="stripe" value="stripe3">
  <label for="stripe3">条带3</label>
</div>
<button id="calculateBtn">计算金额</button>
<button id="amountBtn">按条带计费的金额：0</button>

document.getElementById("calculateBtn").addEventListener("click", function() {
  var checkboxes = document.getElementsByName("stripe");
  var selectedCount = 0;
  for (var i = 0; i < checkboxes.length; i++) {
    if (checkboxes[i].checked) {
      selectedCount++;
    }
  }
  var amount = selectedCount * 10; // 假设每个条带的费用为10元
  document.getElementById("amountBtn").textContent = "按条带计费的金额：" + amount;
});