A baker is buying sugar to make cakes. She already has 7 cups of sugar. The number of cups of sugar she needs to buy, s, to make C cakes can be determined using the function below.

s=2c-7

The baker also needs to make frosting for the cakes. The number of cups of sugar she needs, s, to make b batches of frosting can be determined using the function below.

s=7.5b

Each batch makes enough frosting for 3 cakes.

Which function can be used to find the number of cups of sugar the baker needs to buy to make C cakes AND the frosting for C cakes?