Within the US Federal Income Tax Form 1040,household tax is computed

a. based upon a marginal tax rate that increases for higher income brackets.

b. based upon a marginal tax rate that remains the same for different income brackets.

c. based upon a marginal tax rate that decreases for higher income brackets.

d. based upon an average tax rate that increases for higher income brackets.

e. based upon an average tax rate that decreases for higher income brackets.