Final answer:
The calculated value of C(1.5) is 45.5, which represents the additional cost of using 1.5 gigabytes of data over the monthly allowance. The provided options do not accurately reflect this calculated value.
Step-by-step explanation:
The cost function for a cell phone data plan is represented by C(x) = 25x + 8, where x is the number of gigabytes used over the monthly allowance and C(x) represents the monthly cost for that extra data usage. To calculate C(1.5), we substitute 1.5 for x in the equation:
C(1.5) = 25(1.5) + 8
C(1.5) = 37.5 + 8
C(1.5) = 45.5
This value represents the additional cost for using 1.5 gigabytes over the monthly allowance. Since the monthly allowance is 2 gigabytes, the total usage in this scenario would be 3.5 gigabytes. It is important to note that none of the options provided (A, B, C, D) correctly states the calculated cost for C(1.5); thus, the correct answer is not listed among the options.