The weekly salary paid to employees of a small company that supplies part-time laborers averages +700 with a standard deviation of +400.

(a) If the weekly salaries are normally distributed, estimate the fraction of employees that make more than +300 per week.

(b) If every employee receives a year-end bonus that adds +100 to the paycheck in the final week, how does this change the normal model for that week?

(c) If every employee receives a 5% salary increase for the next year, how does the normal model change?

(d) If the lowest salary is +300 and the median salary is +500, does a normal model appear appropriate?