What is agathas contribution to gdp?

Consider a pay-as-you-go social security system. Payout to an old person, b, is $120. What should be the minimum population growth rate, such that , each young person does not pay more than $80 for the social security? O A. 50% O B. 12.5% O C. 20% O D. 25% O E. None of the above