1. The given expression is $$8a^3 + 9a^2b^4 + 4an^7 + 5$$. 2. The terms are separated by plus signs: first term $$8a^3$$, second term $$9a^2b^4$$, third term $$4an^7$$, and fourth term $$5$$. 3. The coefficient of a term is the numerical factor multiplying the variables. 4. For the second term $$9a^2b^4$$, the coefficient is $$9$$. Therefore, the coefficient of the second term is $$9$$.