(b) Suppose you were to estimate the model for birthweight that includes both mage and its square: bwght=0+1mage+2magesq+u Question: Based on the figure in (a), what sign would you expect to find for ^1 ? For ^2 ? (c) Estimate the model and check your answer to (b). (You will first need to create the variable magesq.) -genmagesq=mage2=regbughtnagenagesq Question: Is the squared term statistically significant? (d) To get a better visualization of the parabola, create the predicted values from your regression in (b). Questions: Is the turning point in this parabola empirically relevant (are there observations in the range of values above and below it)? What is the (approx..) mother's age that "maximizes" birthweight (in a noncausal sense)