Answer:
a)


b)
Explanation:
Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
Solution
Let put some notation
x=value for right arm , y = value for left arm
x: 102, 101,94,79,79
y: 175,169,182,146,144
The first step is calculate the difference
and we obtain this:
d: 73, 68, 88, 67, 65
Part a
The second step is calculate the mean difference

The third step would be calculate the standard deviation for the differences, and we got:

Part b
The next step is calculate the degrees of freedom given by:

Now we need to calculate the critical value on the t distribution with 4 degrees of freedom. The value of
and
, so we need a quantile that accumulates on each tail of the t distribution 0.05 of the area.
We can use the following excel code to find it:"=T.INV(0.05;4)" or "=T.INV(1-0.05;4)". And we got

The confidence interval for the mean is given by the following formula:
(1)
Now we have everything in order to replace into formula (1):
So on this case the 90% confidence interval would be given by (63.331;81.069).