1-year zero-coupon Corporate yield: 12%

2-year zero-coupon Corporate yield: 15%

1-year zero-coupon Treasury bonds yield: 7%

2-year zero-coupon Treasury bonds yield: 10%

Firms marginal probability of default in the first year:4.46%

Firms marginal probability of default in the second year: 4.24%

Q: what is this firms 2-year cumulative probability of default?

(I calculated 8.69% before, but it was wrong)