A credit card company monitors cardholder transaction habits…

A credit card company monitors cardholder transaction habits to detect any unusual activity. Suppose that the dollar value of unusual activity for a customer in a month follows a normal distribution with mean $250 and variance $391. What is the probability of $300 to $400 in unusual activity in a month?

In a chemical plant, 24 holding tanks are used for final pro…

In a chemical plant, 24 holding tanks are used for final product storage. Four tanks are selected at random and without replacement. Suppose that six of the tanks contain material in which the viscosity exceeds the customer requirements. What is the probability that none of the tanks in the sample contains high-viscosity material? Round your answers to three decimal places (e.g. 0.123).

At a particular intersection with flashing red lights in all…

At a particular intersection with flashing red lights in all directions, only 10% of all drivers come to a complete stop when no other cars are visible. If an individual starts observing this intersection at a particular time, what is the probability that the 12th driver they observe under these conditions is the first to come to a complete stop?