The required return on assets is 18%. The firm can borrow at 12.5%; firm's target debt to value ratio is 3/5. The corporate tax rate is 34%, and the risk-free rate is 4% and the market risk premium is 9.2 percent. What is the weighted average cost of capital?

The Feedback I was given is: Kl = 23.45% = 18% + 1.5 × (18% − 12.5%) × (1 − .34)weighted average cost of capital = 2/5 × 23.45% + 3/5 × (12.5%) × (1 − .34)= 14.33%
And the Ans is: 14.33%.

My questions are: where does the 1.5 or 23.45% come from?