Final answer:
The government debt at the end of a 25-year period can be calculated by subtracting the cumulative surplus from the cumulative deficit and adding it to the initial debt.
Step-by-step explanation:
The question is asking for the government debt based on a series of deficits and surpluses over a period of time. To answer the question, we need to calculate the cumulative deficits and surpluses and subtract them from the initial debt.
In this case, the government runs a deficit of $10 billion dollars each year for ten years, resulting in a cumulative deficit of 10 x 10 = $100 billion. Then, the government runs a surplus of $1 billion for five years, resulting in a cumulative surplus of 1 x 5 = $5 billion.
Finally, the government has a balanced budget for another ten years, which means no deficit or surplus. Therefore, the government debt at the end of the 25-year period is the initial debt plus the cumulative deficit minus the cumulative surplus: $3.5 billion + $100 billion - $5 billion = $98.5 billion.