Calculation question after applying bit stuffing

[iimkerry]

Here is one question, i swear this is not my assignment or homework (have encounter replies saying unproductive stuffs like you should attempt your own homework ! It is some past year paper i'm attempting to prepare for upcoming exams )

Question : HDLC uses synchronous transmission. The frame structure consists of a
starting flag (8 bits), address field (8 bits), control field (8 bits), variable
data field, FCS field (16 bits) and ending flag (8 bits). Suppose station A
wants to transmit to station B the following data bits:

1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0

There is 2 part to this question though,

(1) Apply the bit stuffing rule (left to right) to the above data string
to produce the output string.

I did the bit stuffing which was to add a '0' after every 5 '1's. So the final product consist of 7 additional bit from the bit stuffing.

(2) If the output string is transmitted over a 10 kbps communication
line in one HDLC frame, determine the effective data rate of the
transmission.

Here is the part that i do not understand. Literally the input string is 40 bits, but according to the question and by adding all the bits in the frame structure gives 48 bits (don't really understand why the difference here ..) Lastly, how to go about calculating the effective data rate ?


Any help is appreciated here !