Gains 5 seconds in 3 minutes. So, speed of clock = 185/180 = 37/36 to a coreect clock.
Distance moved = 7 am to 4:15 pm = 9 hrs 15 mins = 555 mins.
Distance moved by a correct clock = 555 * 36/37 = 15 * 36 = 540 minutes = 9 hrs.
So, correct time is 4 pm.