1. The data set nbasal. dta contains salary information and career statistics for 269 players in the National Basketball Association (NBA). a. Estimate a model relating points-per-game (points) to years in the league (exper), age, and years played in college (coll). Include a quadratic in exper; the other variables should appear in level form. Report the results in the usual way. Use heteroskedasticity-robust standard errors. b. Holding college years and age fixed, at what value of experience does the next year of experience actually reduce points-per-game