Labor economists have extensively researched the determinants of earnings. Investment in human capital, measured in years of education, and on the job training are some of the most important explanatory variables in this research. You decide to apply earnings functions to the field of sports economics by finding the determinants for baseball pitcher salaries. You collect data on $455$ pitchers for a particular baseball season and estimate the following equation using OLS and heteroskedasticity$-$robust standard errors: