Jackson's Plastic is considering purchasing a new plastic mixer for one of its workshops. The price of the mixer is $$400,000$ and Jackson's plans to borrow $100\%$ of the needed funds from a local bank at $8\%$ after$-$tax cost of debt. Jackson's WACC and cost of equity are $15\%$ and $\%20,$ respectively. What is the appropriate discount rate for Jackson's to evaluate the NPV of this purchase?

$15\%$

$20\%$

$8\%$

We need to know the firm's tax rate to answer