A] The cars have the bumpers with a larger surface area and this is because it leads to less impact of force by anything in opposite direction. If it is not so, the impact would be more causing some destruction in car.
B] Energy = F.s = m.a.s
Power = E/t = m.a.s/t = m.a.v (a=g=10m/s)
Total Power of crane = (500+300)(0.2)(10) = 1600W
Power of Resistance = 1200(0.2)(10) = 2400W
So, the power required to raise the load = 2400-1600 = 800W