What’s a good free response answer to

When it is 4: 00 a.m. in halifax, it is 1: 00 p.m. in karachi, and when it is 9: 00 a.m. in karachi, it is 5: 00 a.m. in warsaw. mary left halifax to fly to karachi, but she accidentally left her watch on warsaw time. according to mary’s watch, she left halifax at 9: 40 p.m. on monday. the local time when she arrived at karachi was 3: 00 p.m. tuesday. how long was mary’s flight? a. 9 hours, 20 minutes b. 13 hours, 20 minutes c. 14 hours, 20 minutes d. 17 hours, 20 minutes