A grocery store has advertised a sale on ice cream. Each box of any flavor of ice cream costs $3.79.

a. If Millie buys one box of strawberry ice cream and one box of chocolate ice cream.
Let S be the number of strawberry ice cream boxes and C be the number of chocolate ice cream boxes.
Write an algebraic expression that represents the total cost (= total Cost) of buying the ice cream. (Be sure to include the two variables: S and C).

b. Write an equivalent expression for your answer in part (a).

c. Explain and show how the expressions are equivalent.