Normal Curve Approximation

A 56-question multiple choice test has 4 possible answers for each question and a student chooses the answers to each problem at random. A student selects 16 correct answers. Find the probability of the result using the normal curve approximation to the binomial distribution.

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... guessing wrong=3/4

Prob(getting m right) = (n!/((n-m)!m!)) p^m q^(n-m)

Where in our case we get:
(56!/(40!16!))x(1/4)^16 x (3/4)^40
The Gaussian approximation ...