Abuilding casts a 16-foot shadow. a 6-foot man standing next to the building casts a 2.5-foot shadow. what is the height, in feet, of the buildings

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?