Using the tax rate schedule given here, perform the$$ following:

a$.$ Find the marginal tax rate for the following levels of sole proprietorship earnings before$$ taxes: $$16,500$; $$58,900$; $$90,700$; $$160,000$; $$230,000$; $$447,900$; and $$1$ million.

b$.$ Plot the marginal tax rates$($measured on the $$y$-$axis$)$ against the pretax income levels$($measured on the $$x$-$axis$).$