ROI as a financial ratio is calculated as follows:
ROI = Net profit/Total investments
In the current case,
Net profit = Net operating income = $700,000
Total investments = Operating assets = $600,000
After purchasing the new machine,
Total investments = 600,000*1.08 = $648,000
Therefore, the new ROI is;
ROI = 700,000/648,000 ≈ 1.08 = 108%