W = Total Capital = $100,000 (That is Total Weight of Capital : Debt + Preferred Share + Equity)
d = Debt = 20% of total ccapital or $20,000
r = Interest rate of d (Debt) 4%
t = tax rate 25%
p = preferred share = 10% of total capital or $10,000
r = Rate of Return of preferred share 7%
e = Equity (Common Share) = 70% or 70,000
D = Dividend on equity e (equity) 10%