commodity forward confusion

sorry if this has been asked before. But I got really confused by Schweser Notes book 4 page 59. Fo,t=So,t * e to the power of [(-Rf) *T] I basically don’t understand the whole page… first how the author got it, second what’s the logic behind it? Thanks for your answers!

I think there is something very strange about schweser’s notation here. I faced the same problem and studied it from the CFAI book. Became perfectly clear after that.

S(0,T) actually means expected spot price at time T. This explains why we have e^(-Rf *T)