Bit times and propagation delay Nodes A and B are accessing a shared medium using CSMA/CD, with propagation delay
of 245 bit times between them (i.e., propagation delay equals to the amount of time to transmit 245 bits). Minimum frame size is 64 bytes. Suppose node  begins transmitting a frame at  = 0 bit time. Before A finishes, node B begins transmitting a frame. Assume no other nodes are active.

What is the latest time by which B can begin its transmission?

Attempt:
Considering that t=512 bit times is the time at which A finishes transmission, shouldn't the latest time by which B begins its transmission be at t=245 bit time? (At t=1, 1st bit is pushed on the link, and at t=245 bit time, this is the last "timing" that B can start transmitting before it senses that A is transmitting). However, the answer given is 244 bit time and I do not understand why.
I would say that at t=0 the first bit would begin getting pushed on the link, which would imply that the 245th bit would begin getting pushed at t=244. Thus you'd want to start pushing at t=244. 

Disclaimer: I know nothing of networking and little of comp sci but hey, I thought I'd give the logic a whirl. I could be completely wrong.