1. Let's understand the problem: We have a Plan A which has a fixed monthly fee of 50 plus a cost of 0.70 per minute used, where $m$ is the number of minutes. 2. The total cost $C$ can be expressed as the sum of the fixed fee and the cost per minute multiplied by the number of minutes: $$C = 50 + 0.70m$$ 3. We need to find the equation that models the cost after 100 minutes, so substitute $m = 100$: $$C = 50 + 0.70 \times 100$$ 4. Calculate the cost: $$C = 50 + 70 = 120$$ 5. From the options given: - A. $C = 70 + 50m$ (incorrect order and values) - B. $C = 0.70 + 50$ (ignores minutes) - C. $C = 50 + 70m$ (incorrect multiplication by 70 instead of 0.70) - D. $C = 50 + 0.70(100)$ (correct for 100 minutes) Therefore, the correct equation modeling the cost after 100 minutes is option D. Final answer: $C = 50 + 0.70(100)$