Compared to a competitive labor market, a monopoly union has employment and a wage. O higher; higher O higher: lower lower; higher lower; lower A monopoly union chooses the wage understanding that the firm responds to the wage by choosing employment competitively. to minimize labor costs. along its labor demand curve. along the labor supply curve. A union bargains with a monopsony employer for an hourly wage of $20 per worker. As a result, the employer's marginal-labor-cost curve becomes perfectly elastic at $20 per worker over the range of employment from zero to up to the quantity supplied of labor at w=20. shifts up by $20 per worker. shifts up by the difference between $20 and the monopsony wage. O shifts left by $20