Which of the following statements regarding the unrelated business income tax is not correct?

a. Unrelated business income is income from activities not related to the exempt purpose of the organization.

b. The unrelated business income tax is levied because the exempt organization is engaging in substantial commercial activities unrelated to its exempt purpose.

c. A flat 30% tax rate is applied to unrelated business taxable income.

d. If the unrelated business income tax were not levied, taxable organizations would be placed at a substantial disadvantage when trying to compete with the exempt organization.