The first group of Mexican immigrants arrived at U.S. in 1960. They were at the age of 20 and earned $30,000. After 40 years of experience in the U.S., their salary increased from $30,000 to $60,000 in 2000. The second group of Mexican immigrants arrived at U.S. in 2000. They were at the age of 20 and earned $20,000 in 2000.a. What is the return from one year of experience for the first group of immigrants? (Assume that the linear relationship between the years of experience and the earnings)b. Suppose that what we observe in 2000 is the earnings of the first and the second immigrants and their ages in 2000. What is the return from one year of experience calculated by this information?