Answer:
It will represent the slope of the graph
Explanation:
Here, we are interested in getting what the cost per mile driven represent
From the information, we can represent the cost as;
C = 15d + 39
In this case we have a representation of the cost using the fixed daily cost(y-intercept) and the cost depending on the number of miles driven which will change based on the number of miles.
Since it is changing, it represents the slope of the function for cost