1. **State the problem:** We have two parking plans, A and B, each with a fixed monthly fee plus a cost per day parked. We want to find the system of equations representing the total cost $C$ for $n$ days parked. 2. **Plan A:** Given as $C = 55 + 21n$ where $55$ is the fixed fee and $21$ is the cost per day. 3. **Plan B:** We have a table of costs for different days: - For $n=3$, $C=106$ - For $n=10$, $C=260$ - For $n=18$, $C=436$ - For $n=20$, $C=480$ 4. **Find Plan B's fixed fee and cost per day:** Assume $C = a + bn$. 5. Use two points to find $a$ and $b$: From $n=3$, $106 = a + 3b$ From $n=10$, $260 = a + 10b$ 6. Subtract equations: $260 - 106 = (a + 10b) - (a + 3b)$ $154 = 7b$ $b = \frac{154}{7} = 22$ 7. Substitute $b=22$ into $106 = a + 3(22)$: $106 = a + 66$ $a = 106 - 66 = 40$ 8. So Plan B is $C = 40 + 22n$. 9. **Compare with options:** - Plan A: $C=55 + 21n$ - Plan B: $C=40 + 22n$ 10. The correct system is option c: A. $C=55 + 21n$ B. $C=40 + 22n$