A salesperson earns commission on the sales that she makes each month. 
The salesperson earns a 5% commission on the first $5,000 she has in sales. 
The salesperson earns a 7.5% commission on the amount on her sales that are greater than $5,000. 
A)This month the salesperson had $8,000 in sales. What amount of commission, in dollars, did she earn? 
B)The salesperson earned $1,375 in commission, last month. How much money, in dollars, did she have in sales last month?