Model:

log(wage)=β0+β1 educ+β2 exper+β3 expersquare+ u

Q1： what`s the approximate return to the fifth year of experience and to the tenth year of  experience?
Q2：At what value of exper does additional experience actually lower predicted log(wage)?

这两个问题问的都是预测值的问题吧？在STATA里面用什么command才能得出这个值呢？