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 +18.95, where M is the number of miles driven. The company also offers an option to ensure the car against damage. The insurance charge I (in dollars) is given by the function I= 0.15 M + 5.70
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.
C=
What does ac equal?? ^^