Consider a firm that spends $$600$ to produce goods in period $1.$ In period $2,$ it sells half of those goods for $$350,$ but its customers pay their bills with a delay, so payment is not received until one period later. In period $3,$ it sells the other half of the goods for $$450,$ and it collects payment on these sales in period $4.$ Calculate the net cash flow for this firm in period $3.$