A link layer protocol carries information in one direction on a full$-$duplex channel. The frame header starts with a $2-$byte marker sequence, then has $2$ bytes for the number of data bytes in the frame, then a byte containing $2$ bits for the frame type and a $6-$bit sequence number. The trailer has a $16-$bit CRC$,$ calculated on all the bytes after the start marker. An acknowledgement frame has the same structure, but no data. The physical layer can carry $60$ Mbit$/$s in both directions at the same time. In each direction, the propagation delay is $800$ s and the probability of bit error is $310-6.$ a$)$ Calculate the optimum number of data bytes in a frame, to maximise the throughput. $(40\%)$ b$)$ Calculate the throughput that will be achieved if all frames carry the optimum number of bytes. If you have not been able to calculate that optimum, assume each frame has $500$ data bytes. $(30\%)$ c$)$ Is the range of sequence numbers adequate? Would the sender ever have to stop and wait for an acknowledgement? Is there any small change that you would suggest to improve this protocol?