Here is the answer:
Given that the sales representative is earning $12 per hour, and he works for 20 hours, this means that he has earned a total of $240 for the hourly basis only. For the units, each unit is $15 and if he has sold 15 units, this would be a total of $225. In total, he has earned $465 in 20 hours with 15 units sold. The answer is the last option.