Debt = 300,000
Equity = 700,00
Weight of debt = 0.3 and weight of equity =0.7
Since the bonds are selling at par, YTM = coupon rate = 7%. The after tax cost of debt = 7%*(1-0.25) = 5.25%
Cost of equity as per CAPM = rf +beta*(Rm-rf) = 4% + 1.2*(8-4) = 8.8%
WACC = 0.3*5.25 + 0.7*8.8 = 7.735%