Subject: mathqa
Question: a man covers a certain distance q in a train . if the train moved 4 km / hr faster , it would take 30 min less . if it moved 2 km / hr slower , it would take 20 mins more . find the distance ?
Option: 
A: 20 km
B: 80 km
C: 60 km
D: 50 km
Answer: C