The surface area of a cylindrical can is given by the function g(r) = 2π​r2 + 6πr, where r is the radius. If f(r) = 2π​r2 gives the total area of the two circular ends, which combined function gives the surface area of the side of the cylinder?

A cylinder with radius r and height 3 inches. A. F + g
B. F – g
C. G – f
D. F · g