A shipping company charges based on calculations of the volume of a rectangular box and the sum of the dimensions of the box. A square rectangular prism has a side length represented by the linear function f(x), and a height represented by the linear function g(x). Which statement describes the combined functions V(x) and S(x)? The volume function is linear but the sum function is not. The sum function is linear but the volume function is not. Both the volume function and the sum function are linear. Neither the volume function nor the sum function is linear.