Frank and gertrude mow lawns for extra money over the summer. frank's income is determined by f(x) = 5x + 15, where x is the number of hours. gertrude's income is g(x) = 4x + 20. if frank and gertrude were to combine their efforts, their income would be h(x) = f(x) + g(x). assume frank works 4 hours. create the function h(x), and indicate if frank will make more money working alone or by teaming with gertrude