We have seen that, for a binomial distribution with $n$ trials, each with probability of success $P$, the mean is as follows:
$$
\mu_X=E[X]=n P
$$
Verify this result for the data of Example 4.7 by calculating the mean directly from
$$
\mu_X=\sum x P(x)
$$
showing that for the binomial distribution, the two formulas produce the same answer.