Answer: 1.54 %
Explanation:
Assuming no risk, the interest rate on the debt can be calculated using the Cost of Equity of levered Capital formula which is,
Cost of Equity of Levered Capital = Un levered cost of capital + Debt / equity * (rate of return - rate of debt)
All the variables are present except the rate of debt.
Plugging them in is,
0.125 = 0.091 + 0.45 ( 0.091 - rD)
0.125 = 0.091 + 0.04095 - 0.45(rD)
0.125 = 0.13195 - 0.45rD
0.45rD= 0.13195 - 0.125
0.45rD = 0.00695
rD = 0.00695/0.45
rD = 0.01544444444
rD = 1.54%
1.54% is the interest rate on the debt.