Hi everyone, I'm taking an entry level software programming class and am having to write a fairly simple code but can't seem to get it to compute right. This is what my code looks like as of now.

<html>
<head></head>
<body>
Welcome to Cheap Beds, Inc.! Please answer the following questions so we know how much to charge our customers.
<br/>

<script type="text/javascript">

var Origprice;

Origprice = prompt('Enter the Original Price of the bed');

var DelivFee;

DelivFee = prompt ('How much are we charging for delivery?');

var credit;

credit = prompt ('How much are we crediting for their old unit?');

var Newcost;

Newcost = (parseInt(Origprice) + parseInt(DelivFee));

var Finalcost;

Finalcost = (parseInt(Newcost) - parseInt(DelivFee));

alert("The bed that was chosen will cost" + Finalcost + " Including delivery fee and trade-in credit for their old bed");


</script>

</body>
</html>

The cost of the bed that I'm entering is 100, shipping is 20 and credit is 5 but at the end it's saying that the price is 100? Does anyone know how I can fix this?