The bandwidth is 10 Mbps, and data packets can be sent continuously.

The link allows infinitely fast transmit, but limits bandwidth such that only 20 packets can be sent per RTT.

Zero transmit time as in (c), but during the first RTT we can send one packet, during the second RTT we can send two packets, during the third we can send four (2^(31)), etc

Consider a point-to-point link 50 km in length. At what bandwidth would propagation delay (at a speed of 210^8m/s) equal transmit delay for 100-byte packets? What about 512-byte packets?