To determine the monthly cost (or slope) from the data provided, we can find the change in cost over the change in time (months).
Let's analyze the data:
- After 1 month, the cost is $74.
- After 2 months, the cost is $99.
- After 3 months, the cost is $124.
- After 4 months, the cost is $149.
We can calculate the monthly cost growth (slope) by looking at the change in cost between months:
-
From month 1 to month 2: \[ \text{Change in cost} = 99 - 74 = 25 \] \[ \text{Change in months} = 2 - 1 = 1 \] Thus, the monthly cost increase (slope) is: \[ \text{slope} = \frac{25}{1} = 25 \]
-
From month 2 to month 3: \[ \text{Change in cost} = 124 - 99 = 25 \] \[ \text{Change in months} = 3 - 2 = 1 \] The monthly cost increase (slope) remains: \[ \text{slope} = \frac{25}{1} = 25 \]
-
From month 3 to month 4: \[ \text{Change in cost} = 149 - 124 = 25 \] \[ \text{Change in months} = 4 - 3 = 1 \] Again, the monthly cost increase (slope) is: \[ \text{slope} = \frac{25}{1} = 25 \]
Since the cost increase has been consistent at $25 for each additional month, the slope or monthly cost is $25.
Therefore, the correct response is $25.