when first packet is transmitted on last link see the scenario
At t=22 it reaches second router
At t=23 it is transmitted from second router
At t=33 it reaches destination
At t=24 second packet is transmitted from second router
At t=34 second packet reaches destination
So every 1 second packet reaches destination.
That means 1st packet reaching destination at 33ms
remaining (60-1=59 packets) can reach the destination with= 59+33 =92ms.
So your analysis is correct Until last step. That means we will not consider the Propagation time for every packet. It should be Transmission time(59*Tt). Hope this helps.