2×3. 14×R× 1=50.24

r = 8；

Surface area = side area+bottom area.

Bottom area = lateral area = 56 ÷ 2 = 28.

Volume = bottom area ÷ 2× h = 28 ÷ 2× 6 = 84

Solution: suppose this pile of coal is x tons.

2.3+ 1/3 x-0.3= 1/2x

X = 12 ton.