can you please just solve part 4 and 5 with steps

Oslo Company prepared the following contribution format income statement based on a sales volume of 1.000 units the relevant range of production is 500 units to 1.500 units): Sales $20.000 Variable expenses 12.000 Contribution margin 8.000 Fixed expenses 6,000 Net operating income S 2,000 Required: (Answer each question independently and always refer to the original data unless instructed otherwise.) 1. What is the contribution margin per unit? 2. What is the contribution margin ratio? 3. What is the variable expense ratio? 4. If sales increase to 1.001 units, what would be the increase in net operating income! 5. If sales decline to 900 units what would be the net operating income