(a) Buoyant force = (mass of liquid displaced) × g
= [10 × 10 × 8 × 0.8 + 10 × 10 × 2 × 1]g
= 840 g
If m is mass of block
mg = 840 g
or m = 840 gm
(b) Pressure at the lower surface of block = pressure at any point on the same level
= 10 × 0.8 × g + 2 × 1 × g
= 10 g = 10 × 9.81
= 98.1 Newton / metre2 .