Aplane left on time at noon on monday. it arrived at its destination at 8: 16 pm the same day which was 16 minutes late on average how many seconds did the plane fall behind every 15 minutes

The right time at which the plane supposed to arrive at its destination = 8:00 pm
but arrived at =8:16 pm
time extra taken = 16 minutes
there are four 15 minutes in an hour  and 32 15 minutes in 8 hours
seconds  the plane was late = 16 x 60
                                             = 960
seconds the plane was late in every fifteen seconds = 960 /32
                                                                                    = 30
(ans) = 30 seconds