Shamrock, Inc., a tax-exempt organization, has $420,000 of net unrelated business income. Total charitable contributions (all associated with the unrelated trade or business) are $60,000. Assuming that the $60,000 was deducted in calculating the $420,000 net unrelated business income, what is Shamrock's unrelated business taxable income? Select one:

a. $360,000.

b. $480,000.

c. $420,000.

d. $432,000.