Chapter 4.3, Problem 26Q

The cross-sectional area of plastic tubing for use in pulmonary resuscitators is normally distributed with $\mu =12.5{\text{ mm}}^2$ and $\sigma =0.2{\text{ mm}}^{\text{2}}$. When the area is less than $12.0{\text{ mm}}^{\text{2}}$ or greater than $13.0{\text{ mm}}^{\text{2}}$, the tube does not fit properly. If the tubes are shipped in boxes of one thousand, how many wrong-sized tubes per box can doctors expect to find?