Subject: mathqa
Question: john purchased some shirts and trousers for $ 1550 . he paid $ 250 less for the shirts than he did for the trousers . if he bought 5 shirts and the cost of a shirt is $ 20 less than that of a trouser , how many trousers did he buy ?
Option: 
A: 4
B: 7
C: 6
D: 5
Answer: C