Clayton is planning to invest up to $\$ 40,000$ in corporate and municipal bonds. The least he is allowed to invest in corporate bonds is $\$ 6000,$ and he does not want to invest more than $\$ 22,000$ in corporate bonds. He also does not want to invest more than $\$ 30,000$ in municipal bonds. The interest is $8 \%$ on corporate bonds and $7 \frac{1}{2} \%$ on municipal bonds. This is simple interest for one year. How much should he invest in each type of bond in order to maximize his income? What is the
maximum income?