11. Specifications for an item call for it to have a strength of at least 900 kilograms per square centimeter. The ingredients and processing that raise the item's strength are expensive, so the intent is to center the process so that the mean strength will be 1,100. The process has a of 100 and is normally distributed.

a. Construct 95 percent control limits for X when samples of size 6 are taken.

b. What portion of production will be below the specifications limit if the process is properly centered?