4. In 2018, Susan had interest expense of $58,500 from her investments. Susan's has investment income of $46,500. Of this amount, interest is $15,000, qualified dividends are $9,000, and a net capital gain on the sale of securities is $22,500. What is the maximum amount of Susan's investment interest expense deduction for the current year if she decides to give up the capital gain preferential treatment?

	a.	$15,000.
	b.	$24,000.
	c.	$37,500.
	d.	$46,500.