A batch of 75 washers contains eight in which the variability in thickness around the circumference of the washer is unacceptable. A sample of 10 washers are selected. If none are unacceptable, then the batch is deemed okay and sent off to purchasing.

2a. What is the probability that none of the unacceptable washers are in the sample?

Probability = __

2b. What is the probability that at least one of the unacceptable washers are in the sample?

Probability = __

The number of telephone calls that arrive at a call center is often modeled as a Poisson random variable. Assume that on average there are ten calls per hour.

a. What is the probability that there are three or less calls in one hour.

Probability =

b. What is the probability that there are 6 or 7 calls in 30 mins.

Probability =