Suppose that at a price of Rs 30 per month there are 30000 subscribers to cable television in small Town. If small Town Cablevision raise its price to Rs 40 per month the number of subscribers will fall to 20000 At which of the following price does small Town Cablevision earn the greatest total revenue ?

A. Rs 0 per month
B. Rs 30 per month
C. Rs 40 per month
D. Either Rs 30 or Rs 40 per month because the price elasticity of demand is 1.0