What is causing this to return NaN?
<p>This is supposed to be a simple order calculator, but for some reason it's just not working. Here's the code:</p>

<pre><code>var name, product, price, discount, quantity;

var name = prompt("What is your name?", "Enter name");
var sentence = "Hello " + name + " please look through our available products and services before placing your order.";
alert(sentence);

var product = prompt("Please enter the name of the product you are looking to purchase from the table.", "Enter product");
var quantity = 1*prompt("How many " + product + " would you like to purchase?", "Enter quantity");

var cost = price * quantity;
var orderdiscount = price * discount * quantity;
var totalcost = cost - orderdiscount;

a = confirm(+ name + ", you ordered " + quantity + " of " + product + ". Is this correct?");

if (a) {
    total = cost - (price * discount * quantity);
        if (product === "ice cream cake") {
                price = 20;
                discount = .15;
        } else if (product === "ice cream cone") {
                price = 3;
                discount = .01;
        } else if (product === "small ice cream sundae") {
                price = 5;
                discount = .05;
        } else if (product === "large ice cream sundae") {
                price = 6;
                discount = .05;
        } else if (prompt = ("Sorry, " + name + ". You entered an invalid product. Refresh the page to reload and place the order again.")) {
        }
        }

else 
{
    alert("Refresh the page to reload and place a new order");
}

document.write("Thank you for placing an order with us, " + name + ".");
document.write("&lt;/br&gt;");
document.write("The cost of buying " + quantity + " of " + product + " is " + cost + ".");
document.write("&lt;/br&gt;");
document.write("The discount for this purchase is " + orderdiscount + ".");
document.write("&lt;/br&gt;");
document.write("With the discount, your total order cost is " + totalcost + ".");
</code></pre>

<p>When I load the page and enter all of the necessary information, it returns:</p>

<p>"Thank you for placing an order with us, .
The cost of buying 1 of ice cream cake is NaN.
The discount for this purchase is NaN.
With the discount, your total order cost is NaN."</p>

<p>There are supposed to be calculated numbers in place of those NaNs. What in this code is causing this to happen?</p>
