Question 1157904
half-interval is t (df=unknown, 0.995)*s/sqrt(n).  Use z first
=2.576*5.2/sqrt(n)=0.55 units hours
13.3952/sqrt(n)=.55
so 13.3952/0.55=sqrt(n)
n=593.16 round to 594


t df=594 should be close to z
divide t 0.995/z 0.995 and multiply by 594
that gives 596 rounded upward.
can check 
t=2.584
t*s/sqrt(586)=.55

596 is the sample size needed.