A car is travelling with varying speed, and at the moment t = 0 the speed is 100 km/h. The car gradually slows down according to the formula L(t) = at bt² , t 0 , where L(t) is the distance travelled along the road and b = 90 km/h2 . The value of a is not given, but you can find it. Using derivative, find the time moment when the car speed becomes 10 km/h. Find the acceleration of the car at that moment.