Answer:
WACC = 5.32%
Explanation:
bond's YTM = 8%
cost of equity = 10%
tax rate = 40%
total bonds = $900,000,000
total common stocks = $100,000,000
total firm's value = $1,000,000,000
to simplify the process I will use hundreds of millions
WACC = (1/10 x 10%) + [9/10 x 8% x (1 - 40%)] = 1% + 4.32% = 5.32%