Johnson Tools produces hammers. It has signed a labor contract that guarantees its 1,000 workers a minimum of 30 hours per week of work. The contract also doubles the regular $20 per hour wage for overtime (more than 30 hours per week). Johnson's production technology uses only one variable input, labor. The company can produce two hammers per hour of employed labor. What is its variable cost function (assuming it cannot hire additional workers)? Graph its variable cost curve.