Soil infill can be compacted with either a mechanical hand compactor or a machine compactor. What is the required infill layer thickness for each of these compactors? Select one: a. Mechanical hand: 300 mm layers and mechanical machine: 600 mm layers b. Mechanical hand: 100 mm layers and mechanical machine: 150 mm layers c. Mechanical hand: 150 mm layers and mechanical machine: 350 mm layers d. Mechanical hand: 150 mm layers and mechanical machine: 100 mm layers