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I need help with my college level statistics for economics class.

3. (28 points) Suppose 30 year olds who have college degrees have an average wage of $50 / hour with a standard deviation of $20 / hour, and their wages are normally distributed. Suppose 30 year olds without college degrees also have normally distributed wages, but their average is $30 / hour with a standard deviation of $10 / hour. Seventy percent of 30 year olds have high school degrees, and 30 percent have college degrees. (a) (5 points) What is the probability that a 30 year old with a college degree earns less than $40/hour? (b) (5 points) What is the probability that a 30 year old without a college degree earns less than $40 / hour? (c) (9 points) You randomly choose a person who earns less than $40/hour. What is the probability he has a college degree? (d) (9 points) You have a sample of 100 people. It turns out that precisely 30 of them have college degrees, and precisely 70 do not. Let Y be the average wage of all 100 people. So Y can be expressed in the following way: Y = 2:1 Ci 'l' 297021 hj 100 Where 01,02, . . . , 030 are the 30 randomly chosen people with college degrees and h1, h2, . . . , hm are the 70 randomly chosen people without college degrees. Find E [E7] and 037