A telephone company in a town has 500 subscribers on its list and collects fixed charges of Rs 300 per subscriber. The company proposes to increase the annual subscription and it is believed that every increase of Rs 1 one subscriber will discontinue the service. Find what increase will bring maximum revenue?

Explanation

To solve the problem, we need to find the increase in subscription that will maximize the revenue for the telephone company. Let's break down the solution step by step.

### Step 1: Define the Variables
Let:
- \( x \) = increase in subscription fee (in Rs)
- The current subscription fee = Rs 300
- The current number of subscribers = 500

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