Compute the z scores of 12.22 and 12,28 ounces, they are:

z1 = (12.22-12.32)/0.04 = -2.5

and:

z2 = (12.28-12.32)/0.04 = -1

Now look these up in a table of the cumulative standard normal distribution:

P(z<z1) = P(z<-2.5) = 0.0062

P(z<z2) = P(z<-1) = 0.1587

So:

P(z1<z<z2)= P(z<z2) - P(z<z1) = 0.1587 - 0.0062 = 0.1525

RonL