Question 1059759
The interval width is z*sigma/sqrt (n)=2; z(.995)=2.576. 
Square everything 
4=2.576^2*10.2^/n
N=690.386/4
=172.59 or 173
With 95%, z=1.96 and its square is 3.8416
The smaller value will lessen the numerator and decrease the sample size (to 100). 
Less confidence with no other changes will cause a smaller sample size.