Which of the following is the most profitable investment for a game shop earning $2 profit from every game sold?
Vehicle with $120 daily operating cost, delivering 80 games per day

Inventory software with $10 daily operating cost, saving 30 games per day from theft

Game cleaning system with $5 daily operating cost, increasing sales by 15 games per day

Electronic billboard with $20 daily operating cost, increasing sales by 20 games per day