Consider the data ceosal1 in the R package "wooldridge". NOTE: prepare your answers of the following questions using the sub-sample between 13-th and 202-th observations (Use ceosal1[13:202,] to obtain the sub-sample dataset for this question

Use log(sales) and all sector variables as the IV's (you can select the base group to be omitted), and use log(salary) as the DV.

a) With 1% increase in sales, what is the percentage change in the average of a CEO's salaries, everything else equal? Round your answer to 2 decimal places.

b) Is the coefficient of log(sales) statistically significant at the 0.1% significance level?

c) How many "%" more is the average salary of a consprod CEO compared with a utility CEO? Use a negative number if the former's salary is lower than the latter. Round your answer to 2 decimal places.

Use R Codes to solve the question.