A car rental company's standard charge includes an initial fee plus an additional fee for each mile driven. The standard charge S (in dollars) is given by the function S=0.40M+16.95, where M is the number of miles driven. The company also offers an option to insure the car against damage. The insurance charge I (in dollars) is given by the function 10.25M +3.90.
Let C be the total charge (in dollars) for a rental that includes insurance. Write an equation relating C to M. Simplify your
answer as much as possible.