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+15.75, where M is the number of miles driven.
The company also offers an option to insure the car against damage. The insurance charge 1 (in dollars) is given by the
function 1=0.15M+5.80.
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.