i believe it would be 9:48 because it takes 2 minutes to go up one step, since 1 minute he goes up 4 then goes down 3 the next minute, leaving the only progress of the 2 minutes is 1 step.
So 2 minutes for 1 step, 24 steps would be 24x2 =48 and 9:00 48 minutes later is 9:48