$($cumulative$)$ A government is thinking about undertaking a restoration project of a polluted river that will cost $500,000$ dollars now. The government has spent $100,000$ dollars on this river five years ago. If the government does not spend the money, it can invest the $500,000$ dollars for one year. Given this information what would an economist say is the opportunity cost in dollars of spending the money now to restore the polluted river if the interest rate is $0\%$

A$.0$

B$.600,000$

C$.500,000$

D$.$ None of the above