help on probabilities

Roger has read a report that the weights of adult mail Siberian tigers have a distribution which is approximately normal with mean μ = 390 lb and σ = 65 lb.
a) Find the probability that an individual male Siberian tiger will weigh more than 450 lb.
b Find the probability that a random sample of 4 male Siberian tigers will have a sample mean weight more than 450 lb.
Rachel, first convert 450 to a z-score. z=(x-mean)/s.d. (450-390)/65 = .923
then look up this score in the unit normal table to obtain the probability of getting a tiger that weighs > 450. The p(450)= .1788.
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