If a country's debt-to-GDP ratio if currently 50% and its debt is expected to grow from $40 trillion to $50 trillion in the next 5 years, what will the country's GDP have to be in 5 years to maintain the current debt-to-GDP ratio?
a. 80 Trillion $
b. 25 Trillion $
c. 20 Trillion $
d. 100 Trillion $