The US recently purchased $1 billion of 30-year zero-coupon bonds from a struggling foreign nation. The bonds yield 4.5% per year interest. Zero coupon means the bonds pay no annual interest payments. Instead, all interest is at the end of 30 years. A US senator objected, claiming that the correct interest rate for bonds like this is 7.25%.

The result, he said, was a multimillion dollar gift to the foreign country without the approval of congress. Assuming the senator's rate is correct, how much will the foreign country have saved in interest?

Could you please make a cash flow diagram showing clear and specific instructions.