The cell phone plan from Company C costs $10 per month, plus $15 per gigabyte for data used. The plan from Company D costs $80 per month, with unlimited data.

Rule C gives the monthly cost, in dollars, of using g gigabytes of data on Company C’s plan.

Rule D gives the monthly cost, in dollars, of using g gigabytes of data on Company D’s plan.

a. Write a sentence describing the meaning of the statement C(2)=40 .

b. Which is less, C(4) or D(4)? What does this mean for the two phone plans?

c. Which is less, C(5) or D(5)? Explain how you know.

d. For what number g is C(g)=130?