please explain

44. In 2020. Casmir earned $9,000 in net investment income and incurred $14,000 of investmen interest expense. Casmir paid off the loan in early 2021, so he only paid $2,000 of investment interest expense in 2021. He earned $10,000 of net investment income in 2021. How much investment interest expense can Casmir deduct in 2021? A) $2,000 B) $10.000 C) $7,000 D) SO