$(30$ pts$,$ chapter $8-2$ Example $3)$ Consider using TDM to multiplex $4$ sources, each having $100kbps$ data rate. If the interleaved unit is a byte $(8$ bits$)$ and $1$ framing bit is added to each frame,

a$)$ what is the frame rate $($hint: frame rate is not necessarily equal to bit rate, instead, is always equal to unit rate$)?$

b$)$ what is the frame duration?

c$)$ what is the number of bits per frame?

d$)$ what is the total bit rate of the transmission link $($Hint: frame rate times the # of bits per frame$)?$