The sender sends 5 packets to the receiver using RDT3.0. The third packet has a very long delay, but its ack arrives just after the timeout. There are no errors, losses, or long delays after that. That is, all packets and acks are correctly received without triggering a timeout.

(a) Draw a diagram showing how these 5 packets are sent out. How many packets does the sender send in total?
(b) Is there a fatal flaw in RDT3.0? If so, please provide an example. If not, could you please explain why?