Sen has $100 of outstanding debt, on which it pays an interest rate = 15%/year. Its corporate income tax rate = 20%. Its full income statement is as follows:

Revenues $400

COGS $300

Expenses $ 80

EBIT $ 20

Interest $ 15

EBT $ 5

Tax @ 20% $ 1

Net Income $ 4

What is the dollar value of Sen's interest tax shield?