Token ring protocol Efficiency and Cycle time?

Question

I read Token ring protocol from a book Forouzon.

According to book,

Let N be the number of stations in the ring, THT the token holding time, Tt be the transmission time of packet, Tp be the propagation time of packet on Channel/ Link.

Then Cycle Time = n * THT + Tp (this is cycle time for token)

and efficiency = (useful time)/(Cycle Time)

Here useful time is stated as N * Tt. (justified as transmission time at each station in single cycle of token passing)

And thus proven efficiency = (N * Tt)/(n*THT + Tp)

My question is: why not this (N*Tt) is added in Cycle time?

so the efficiency could become efficiency = (N * Tt)/(n*THT + Tp +N * Tt)

Answer 1

Yes. But it has already been included.

Token Holding time is THT = Transmission Time + Ring Latency time (for single round of packet transmission)

As (THT = Tt + Tp) .