A 1.5−kg block moves to the right and hit a 2-kg block that is initially at rest on a horizontal surface. After the collision, the 1.5−kg block slides to the left with a speed of −5 m/s, and the 2−kg block slides to the right for 7.5 m before coming to rest. The coefficient of kinetic friction between the block and the surface is 0.6. (a) What is the frictional force exerted on the 2 kg-block when it is sliding? (b) What is the speed of the 2−kg block immediately after its being hit by the 1.5−kg block? (c) What was the speed of the 1.5−kg immediately before the collision?