A company has two large computers. The slower computer can send all the company's email in 45 minutes. The faster computer can complete the same job in 15 minutes. If both computers are working together, how long will it take them to do the job?

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 of her sales that are greater than $5,000. this month the sales person had $8,000 in sales. what amount of commission, in dollars, did she earn?