Wait time when ordering a pizza are normally distributed wit

Wait time when ordering a pizza are normally distributed with a mean of 68.2 minutes and standard deviation of 14.8 minutes.

a)What is the probability that waiting time is exactly 30 minutes?

b)What is the probability that waiting time is between 60 and 80 minutes?

c)Ninety percent of customers will wait more than what amount of time for a pizza?

Best Answer must include the formula used to solve, and details, step by step. Appropriate level for an Introduction to Statistics class.

a)What is the probability that waiting time is exactly 30 minutes?

P(X=30) = P(29.5<X<30.5)

=P((29.5-68.2)/14.8 <(X-mean)/s <(30.5-68.2)/14.8)

=P(-2.61<Z<-2.55)

=0.0009 (from standard normal table)

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b)What is the probability that waiting time is between 60 and 80 minutes?

P(60<X<80) = P((60-68.2)/14.8<Z<(80-68.2)/14.8)

=P(-0.55<Z<0.8) =0.4970 (from standard normal table)

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c)Ninety percent of customers will wait more than what amount of time for a pizza?

P(X>c)=0.9

--> P(Z<(c-68.2)/14.8)=1-0.9=0.1

-->(c-68.2)/14.8 =-1.28 (from standard normal table)

So c= 68.2 -1.28*14.8 =49.256