$1.$ Data on working men was used to estimate the following equation:

Where, sibs $=$ siblings ; meduc $=$ mother education and feduc $=$ father education

$$ N$=722,$ R$2=0\mathrm{.}214$

$$ I.$$ Does sibs have the expected effect? Explain. Holding meduc and feduc fixed, by how much does sibs have to increase to reduce predicted years of education by one year? $($A non$-$integer answer is acceptable here.$)(5$points$)$

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$$ II$.$ Discuss the interpretation of the coefficient on medec. $(5$points$)$

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$$ III.$$ Suppose that Man A has no siblings, and his mother and father each have $12$ years of schooling. Man B has no siblings, and his mother and father each have $16$ years of schooling. What is the predicted difference in years of education between and B$?(10$points$)$