Answer :
Answer:
decreased by $150 billion
Explanation:
Given that
Year 1 = + 80 billion
Year 2 = + 120 billion
Year 3 = - 10 billion
Year 4 = - 40 billion
Where
+ and - represents surplus and deficits respectively
Therefore,
Net budget surplus = 80 + 120 - 10 - 40
= 200 - 50
= $150 billion
In the question, it was assumed the budget surplus was used in paying down public debt, thus
Public debt decreased by $150billion