Peter decided to rake the garden next to the house. He used a 3 kg shovel. On average, with one swing, he covers a square of soil 20 cm long, 15 cm wide and 30 cm deep. He raises the shovel with the soil by 40 cm (ie from the initial position of the soil: 15 cm below the soil surface, to the maximum height: 25 cm above the soil surface) and turn the soil.
a) How much work does Peter do to rake a rectangular beam 4 m long and 3 m wide? The density of the soil is 1500 kg / m3
b) With what power does he work if he does the work in one hour