Labor Economics describeed in this answer
Assume that the demand curve for labor in country Y is w = 100 - 4E, where E is measured as millions of workers. Prior to immigration, there are 20 million workers in the country. Suppose that there is an influx of 1 million immigrants into country Y. Assuming that labor accounts for 80% of country Y's gross domestic product, find out immigrant surplus as a share of national income.