The phone company B-Mobile has a monthly cellular plan where a customer pays a flat fee for unlimited voice calls and then a certain amount per GB of data used. If a customer uses 8 GB, the monthly cost will be $48. If the customer uses 38 GB, the monthly cost will be $108. A) Find an equation in the form y = m x + b , where x is the number of GB of data used in a month and y is the total monthly cost of the B-Mobile plan.

y = __________

B) Use your equation to find the total monthly cost if 18 GB are used.

Answer: If 18 GB are used, the total cost will be _______ dollars