It was found that when the brakes of a vehicle were applied,the breaking distance,d meters,is proportional to the square of its speed,v km/h. Find the relationship between d and v. Then,find the break

It was found that when the brakes of a vehicle were applied,the breaking distance,d meters,is proportional to the square of its speed,v km/h. Find the relationship between d and v. Then,find the breaking distance when the speed is 72 km/h.