A graphing calculator is recommended.

A 20-gallon barrel is filled completely with pure water. Salt water with a concentration of 0.3 lb/gal is then pumped into the barrel, and the resulting mixture overflows at the same rate. The amount of salt in the barrel at time t is given by Q(t) = 6(1 − e−0.02t) where t is measured in minutes and Q(t) is measured in pounds.

How much salt is in the barrel after 3 min? (Round your answer to two decimal places.)

Arandom sample of 15 observations is used to estimate the population mean. the sample mean and the standard deviation are calculated as 172 and 63, respectively. assume that the population is normally distributed. a. with 99 confidence, what is the margin of error for the estimation of the population mean? b. construct the 99% confidence interval for the population mean. c. construct the 95% confidence interval for the population mean. d. construct the 83% confidence interval for the population mean. hint: you need to use excel function =t. inv.2t to find the value of t for the interval calculation.