1. Test whether edu is statistically significant in regression in line 4. What is the economic significance of this estimate?
2. Test whether the wage penalty for being Black is equal to the wage penalty for being married in regression in line 4.
3. Test the joint significance of edu and married in regression in line 4.
4. Test whether returns to schooling differ between blacks and non-blacks.

4 . reg log_wage edu black c.age\#\#c.age married