a block of wood 30 cm by 40 cm by 20 cm has a density of 0.81 g per cm^3. Its corner was chopped by an axe (an equilateral triangle pyramid was chopped off with each side 5 cm), and a section was removed. Find to one decimal place:

a) the remaining volume of the block

b) the surface area of the remaining block

c) the mass of the remaining block