Answer: b. 14 pounds
Step-by-step explanation:
Formula to calculate average :
Let x denotes the number of pounds the last person have to gain so that the group can attain its goal.
Required average = 10 pounds
Observations = 9, 13, 11, 6, 7 and x (pounds)
Number of observations= 6
Sum of all observations = 9+13+ 11+ 6+7+x=46+x
According to the question , we have
i..e the last person has to gain 14 pounds so that the group can attain its goal.
Hence, the correct answer is b. 14 pounds .