When a car is braking, the distance of m it travels after the brakes are applied until it stops consists of two parts: one part varies directly as the time t seconds after the brakes are applied, the other part varies directly as the square of t. If the distance travelled by the car are 60m and 75m when t=2 and t=3 respectively, find the distance it travels when t=4. How to calculate the answer 80?