Answer: The message must be sent 9.313 approximately 9 times to get the entire data through.
Explanations: To find how many times the message must be sent on average to avoid error control in data link later.
E = 1/P
E = The average number of attempt before successful transmission.
P= Total probability of transmission without error.
STEP1 : FIND TOTAL PROBABILITY;
Since it each frame has a probability of 80% to be successful.
For each frame p = 80/100 = 0.8
For the 10 frame; total probability
P= (0.8)^10 = 0.1074
STEP2: FIND THE AVERAGE NUMBER OF OF TRIAL BEFORE A SUCCESSFUL TRANSMISSION WITHOUT ERROR;
Using equation above
E = 1/P
E= 1 ÷ 0.1074 = 9.313
Therefore they must be an average of 9.313 approximately 9 trials before a successful transmission without error.
The answer is A. For example, you could start at slide 8 and jump to slide 2 and then to 3. It does not follow and linear structure!!