Calcium is an essential nutrient for strong bones and for controlling blood pressure and heart beat. Because most of the body's calcium is stored in bones and teeth, the body withdraws the calcium it needs from the bones. Over time, if more calcium is taken out of the bones than is put in, the result may be thin, weak bones. This is especially important for women who are often recommended a calcium supplement. A consumer group activist assumes that calcium content in two popular supplements are normally distributed with the same unknown population variance, and uses the following information obtained under independent sampling: Supplement 1 Supplement 2 x1 = 990 mg x2 = 1,000 mg 81 = 32 mg 82 = 23 mg n1 = 9 n2 = 12 Let #1 and /2 denote the corresponding population means. Construct a 95% confidence interval for the difference #1 - #2. (Round the interval to two decimal places.)