MadeEasy Subject Test 2019: Computer Networks - Sliding Window

Question

How it is coming answer 8 ?

Answer 1

transmission time=(16*10^3)/(64*10^6)
propagation time=(2000*10^3)/((2*3*10^8)/3)

for efficiency to be 100%;

sender window size=1+2(propagation time / transmission time)

                               =81

receiver window size=81;(using SR PROTOCOL)

min sequence no required =81+81=162

min bits in sequence no. fields=8;