Solve the systems of equations. it is necessary to set up the appropriate equations. All numbers are accurate to at least three significant digits.

Under certain conditions, the cost per mile C of operating a car is a function of the speed v (in mi/h) of the car, given by
C = av² + bv + c. If C = 28 ¢ mi for v = 10 mi h,
C = 22 ¢ mi for v = 30 mi h, and C = 24 ¢ mi for
v = 50 mi h, find C as a function of v.