Answer: 
Step-by-step explanation:
Given
Cost of white-washing =Rs. 4989.60
Rate =20 per meter square
So, inside area of = 
The surface area of dome= 

The volume of air in the dome 

I believe it is b)
Because you always do rise over the run and if it goes right then it is positive and if it goes left it is negative.
920,438. 921,438-1,000=920,438