Question 1183701
The 99.9% C.I. is worked out as follows:


{{{(X-bar) +- t[0.9995]*(s/sqrt(n)) = 60 +- (3.437)*(5/sqrt(70))}}} = [57.946, 62.054]


The t-statistic (with d.f. = 69) was used in the construction of the C.I. since technically, no matter what the sample size is, 
as long as the standard deviation of the underlying population is UNKNOWN, the appropriate distribution to use is t. 


Now you can do the intervals with 80% and 85% confidence levels.


(t-probabilities were taken from https://stattrek.com/online-calculator/t-distribution.aspx.)