= Solution
A <disjunctive normal form>, also called a <sum of products>, is an OR of AND terms, each made from <Boolean literals> such as $a$ or $\bar a$. For example,
$$
f(a,b,c)=ab+\bar a c.
$$
Here juxtaposition means <logical conjunction>, $+$ means <logical disjunction>, and a bar means <negation>. The expression need not be canonical: a term can omit variables, and need not name a single row of the <truth table>.
Implement each product by an <AND gate> and combine the products with an <OR gate>. Supply complemented inputs with <NOT gates>. Thus
$$
\boxed{\text{sum of products}\quad\longleftrightarrow\quad\text{AND layer followed by OR layer}.}
$$
This is the usual two-level <combinational logic> realization, counting complemented inputs as available. If <NOT gates> are counted, a complemented input can traverse three gates. The two-level depth statement also assumes sufficiently large gate fan-in: using only two-input <logic gates> requires trees for long products or sums. Constant, single-product and single-literal <Boolean functions> may need fewer levels, so the two-level construction is a general bound, not a claim that every expression requires exactly two layers.
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