Subject: mathqa
Question: tickets to a certain concert sell for $ 20 each . the first 10 people to show up at the ticket booth received a 40 % discount , and the next 20 received a 15 % discount . if 52 people bought tickets to the concert , what was the total revenue from ticket sales ?
Option: 
A: $ 850
B: $ 1,140
C: $ 600
D: $ 900
Answer: D