A 90 kg physics teacher stands on a rotating platform with a 15 kg mass in each hand. With his arms outstretched (each arm is 75 cm long) he spins at a rate of 4 revolutions per second. He brings his arms in, and his speed increases to 9 revolutions per second. What is the ratio of his rotational inertia with his arms out to his rotational inertia with his arms in?