Merrimac Brewing company's total assets equal $$18$ million. The book value of Mernuty is $$6$ million. Excess cash is $$200,000.$ The market value of Merrimac's equity is $$10$ million. It's Debt to Enterprise Value ratio is $\mathrm{.}5.$ What is the book value of Merrimac's interest$-$ bearing debt?

$$13$ million

$$5\mathrm{.}25$ million

$$20\mathrm{.}4$ million

$$15$ million

$$10\mathrm{.}2$ million