An investment costs $640 and offers a payoff of $800 with probability p and 0 with probability 1-p. Time-equivalent Treasuries offer an interest rate of 4%. Assume risk neutrality, i.e. the expected return on any security of the same time duration should be the same regardless of how risky the payoff is.

A: What is the promised return of the investment? 3+ Decimals

B: What is the probability of default? 2+ Decimals