A project requires $$21,000$ of net working capital $($NWC$)$ over its $4-$year life. Which one of these is correct?

Multiple choice question.

There is a cash outflow in year $4$ of $$21,000.$

There is only one cash flow and it is an outflow of $$21,000$ at time zero.

There is a cash outflow of $$5,250$ a year for years $0$ to $3.$

There is no cash flow for NWC in years $1$ to $3.$