We wish to invest between $14,000 and $18,500 on three different assets whose respective annual returns are 20.5%, 22%, and 21.5%. However, the amount invested in investment 2 should not exceed 25% of the total investment, and investments 1 and 2 should account for at least 50% of the total investment. We wish to use linear programming to maximize the annual return from the entire investment. 

Suppose that we have decided to increase our total maximum investment by $ 1000. How much should we expect this additional investment amount to contribute to the optimal return? Round your answer to the nearest whole number and do not include the dollar sign (3) with your answer.