How do I solve this?

4. (12 points) Using the data on 722 working men in Fairbanks, the following equations were estimated: edic = 10.36 - 0.094 sibs + 0.131 meduc + 0.210 feduc 17 = 722 . R- = 0.994 where educ is years of schooling, sibs is number of siblings, meduc is mother's years of schooling, and feduc is father's years of schooling. (a) Holding meduc and feduc fixed, by how much does sibs have to increase to reduce predicted years of education by one year? (A noninteger answer is acceptable here) (3 points) (b) Interpret the coefficient on meduc clearly. Is the sign of this estimate what you expect it to be? (3 points). (c) Suppose that Man A has no siblings, and his mother and father each have 12 years of education. Man B has no siblings, and his mother and father each have 16 years of education. What is the predicted difference in years of education between B and A? (3 points) (d) Would you say sibs, meduc and feduc explain much of the variation in educ? Why or why not? Explain clearly (3 points)