The time length in hours of a certain airplane flight can be represented by the function f(x) = 0.0025x + 0.75, where x is the number of miles for the flight.The time length of another airplane flight in hours can be represented by the function g(x) = 0.004x + 0.5, where x is the number of miles for the flight.Which function represents the sum of the flight time lengths, h(x) = f(x) + g(x)?