Question 918527
 {{{z =blue (x - mu)/blue(sigma/sqrt(n))}}}
 {{{z =blue (x - 100)/blue(20/sqrt(16))}}}
a) z = 4/5, P(x <104) = P(z < 4/5) = normalcdf(-100, .8)
b) z = -2/5  and 4/5
P(98 < x < 104) = P(-.4 < z < .8) = normalcdf(-.4, .8)