$4$A$)$ Distinguish between any two multiplexing techniques with respect to the Analog and digital data.

$4$B$)$ In a CSMA$/$CD network with a data rate of $100$ Mbps $,$ the minimum frame size is found to be $512$

bits for the correct operation of the collision detection process. What should be the minimum frame

size if we increase the data rate to $10$ Gbps$?$

$4$C$)$ A periodic signal has a bandwidth of $45$ Hz $.$ The highest frequency is $80$ Hz $.$ What is the lowest

frequency? Draw the spectrum if the signal contains all frequencies of the same amplitude.