Answer
a) Normal
b) $21.1$
c) $0.57$
Work Step by Step
a) Using our knowledge of distributions, we can see that this distribution is bell-shaped, or normal.
b) The mean of all of the sample means is equal to the mean given in the question, which is $21.1$.
c) We find that the standard deviation is:
$\frac{5.1}{\sqrt{80}}=0.57$
