Frames of 1000 bits are sent over a 1-Mbps channel using a geostationary satellite whose propagation time

Question:

Frames of 1000 bits are sent over a 1-Mbps channel using a geostationary satellite whose propagation time from the earth is 270 msec. Acknowledgements are always piggybacked onto data frames. The headers are very short.
Three-bit sequence numbers are used. What is the maximum achievable channel utilization for?
(a) Stop-and-wait.
(b) Protocol 5.
(c) Protocol 6.