A videotape store has an average weekly gross of $\$1,158$ with a standard deviation of $\$120$. The store’s gross receipts during a randomly selected week follow a normal distribution.

a.) What is the probability of grossing less than $1,000 in a week?

b.) What is the 80th percentile of weekly gross receipts?

Solution:

(a) The probability is

(b) We need to find C such that

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