You buy 20 cupcakes for $15 and are going to sell them for $2 each. You want to write an expression that represents how much money you will make each day that you sell cupcakes. Which of these quantities should be represented with a variable?

the number of cupcakes you bought the number of cupcakes you bought
the amount of money you spent on the cupcakes
the cost of each cupcake sold the cost of each cupcake sold
the number of cupcakes sold

The number of cupcakes sold should be represented with a variable.