Marginal tax rates$$ Using the tax rate schedule perform the$$ following:

a$.$ Find the marginal tax rate for the following levels of sole proprietorship earnings before$$ taxes: $ $13$ comma $000$$$13,000$; $ $60$ comma $900$$$60,900$; $ $90$ comma $900$$$90,900$; $ $149$ comma $000$$$149,000$; $ $247$ comma $000$$$247,000$; $ $449$ comma $100$$$449,100$; and $ $1$$$1$ million.

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