The worker DOES NOT make 120 ornaments in 30 hours, as "the-always-wrong-person"suggests.
Hence, you should know by now that his answer will be 100% WRONG!
4 ornaments every 15 minutes ====> 16 ornaments every hour ====> 16*30 = 480 ornaments in 30 hours ====> the earning is 1.15*480 = 552 dollars in 30 hours.