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.

C(g) = 10 + 15g

C'(g) = 80

The monthly charges of Company C for using 2 Gigabyte of data usage.

Step-by-step explanation:

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.

Now, the monthly cost in Company C for using g gigabyte of data will be  

C(g) = 10 + 15g (1)

Again, the monthly cost in Company D for using g gigabyte of data will be  

C'(g) = 80 (2)

Now, from equation (1), the statement C(2) = 10 + 15 × 2 = 40, means that monthly charges of Company C for using 2 Gigabyte of data usage.

step-by-step explanation: