We have the following:
Part A:
The form of the equation of a line is

Where m is the slope and b is y-intercept
The first thing is to calculate the slope of the equation

The points are (2, 225) and (5, 480)

Now, for b:

The equation is:

Part B:

Part C:
To make a graph of the situation, we must give x values and evaluate them in the previous function.
For example

These points are plotted on the Cartesian plane, where the x-axis represents the days and the y-axis represents the total cost of the rent.