Sky Inc. acquired a piece of machinery on July 1, 2017 and gave a noninterest-bearing note in exchange for the machinery. Sky must pay $645,000 on March 31, 2018 to satisfy the obligation. If Sky accrued interest of 30,000 on its 2017 financial statements, what is the imputed annual interest rate?

a. 5%. b. 7.5%. c. 10%. d. None of these answer choices are correct.