Emily wants to start a cell phone plan with AT&T. The company charges a set-up fee of
$39.99 and a monthly charge of $79.99 for the plan Emily wants to buy. Choose the
equation that models Emily's total cost C after m number of months.
C = 79.99 - 39.99m
O C = 39.99 + 79.99m
C = -79.99 - 39.99m
C = 79.99 + 39.99m