题目:
A salesperson received a 6-percent commission on the amount of total sales up to and including $10,000, and an r-percent commission on the amount of total sales over $10,000. If the salesperson received a total commission of $920 on total sales of $14,000, what was the value of r ?
选项:
A、3.2
B、4.3
C、6.6
D、8.0
E、9.2
答案:
D