The probability mass function of a binomial random variable is given by:
\[f_X(x) = \binom{n}{x} p^x (1-p)^{n-x}\]
where $n$ is the number of trials, $p$ is the probability of success, and $x$ is the number of successes. In this case, $n=3$ and $p=0.25$, so we
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