Suppose that the tax on an income of $20,000 is equal to $4,000.Assume, as well, that the tax would rise to $4,400 if this income were to rise to $22,000.What is the marginal rate of tax implicit?

a. 20 percent.

b. about (but not more than) 21 percent.

c. more than 21 percent, but just under 22 percent.

d. 40 percent.