In the United States, the birth rate $B$ of unmarried women (births per 1000 unmarried women) for women whose age is $a$ is modeled by the function $B(a)=-0.33 a^{2}+19.17 a-213.37$
(a) What is the age of unmarried women with the highest birth rate?
(b) What is the highest birth rate of unmarried women?
(c) Evaluate and interpret $B(40)$