$4.$ We need to use synchronous TDM and combine $20$ digital sources, each of $200$ Kbps$.$ Each output slot carries $2$ bit from each digital sources, but one extra bit is added to each frame for synchronization. Answer the following questions:

A$.$ What is the size of an output frame in bits?

B$.$ What is the output frame rate?

C$.$ What is the duration of an output frame?

D$.$ What is the output data rate?

E$.$ What is the efficiency of the system $($ratio of useful bits to the total bits$)?$