Cant figure out how to get variable expense

Required: (Consider each case independently). 1. What is the revised net operating income if unit sales increase by 18% ? 2. What is the revised net operating income if the selling price decreases by $1.30 per unit and the number of units sold increases by 17% 3. What is the revised net operating income if the selling price increases by $130 per unit, fixed expenses increase by $7,000, and the number of units sold decreases by 75 ? 4. What is the revised net operating income if the seling price per unit increases by 20%, variable expenses increase by 30 cents per unit, and the number of units sold decreases by 13%