Round trip time = 2* Tp (propagation delay) = 50 * 10-6 sec
Transmission time ( Tt)= frame size(L) /Bandwidth (B) = 100 / (100 * 106 ) sec = 10-6 sec
Total window size = 1+ 2* (Tp / Tt )
= 1+ (50 * 10-6 / 10-6)
= 51
No of bits for sequence number = ceil of (log2 51) = 6