Final answer:
The value of the slope for Enterprise Rent-a-Car's pricing model is $0.25 per mile, as it represents the cost increase for every additional mile driven.
Step-by-step explanation:
The question asks for the value of the slope in a linear model describing the charges of Enterprise Rent-a-Car. In this context, the slope represents the rate at which costs increase with every additional mile driven. According to the given information, the company charges a one-time cleaning fee and then $0.25 per mile after that. Therefore, the slope in this model is $0.25 per mile because that is the rate at which the cost increases for each additional mile. In the form of a linear equation y = mx + b, where m is the slope and b the y-intercept, the slope here is the constant rate of change, which is $0.25 for each additional mile driven.