A car rental company's standard charge includes an initial fee plus an additional fee for each kilometer driven. The standard charge S (in dollars) is given by the function =S+18.950.40K, where K is the number of kilometers driven. The company also offers an option to insure the car against damage. The insurance charge I (in dollars) is given by the function =I+4.800.25K. Let C be the total charge (in dollars) for a rental that includes insurance. Write an equation relating C to K. Simplify your answer as much as possible.