Question 1197734
 {{{z =blue (x - mu)/blue(sigma/sqrt(n))}}}  
0r
Me = 13, 92  and z = 1.96 ( 95% confidence interval)
 n = {{{ (z*blue(sigma)/ME)^2}}} =  {{{ (1.96*blue(92)/13)^2}}}= 192.4
n = 193 (always round up for sample size)