Solution
= Solution
In the <uniform balls-in-bins allocation>, each ball enters box 1 independently with <probability> $1/n$. Thus \b[$M_1$ has the <binomial distribution> $\operatorname{Bin}(n,1/n)$], with <probability mass function>
$$
\boxed{\mathbb P(M_1=k)=\binom nk\left(\frac1n\right)^k\left(1-\frac1n\right)^{n-k},\quad k=0,\ldots,n,}
$$
and zero outside that range.