Correct Answer - Option 1 : 500 cum.
Calculation:
Given, cost of excavation by manually = Rs. 10 per cum
Cost of the excavation by machine = Rs. 4000 + Rs. 2 per cm
Let the quantity of earth is ‘x’ for which the cost of excavation by machine will be equal to the cost of manual excavation
10x = 4000 + 2x
8x = 4000
x = 500 cum.