Imagine that there is a group of workers, group B, which has an average productivity of $9 per hour. Suppose workers from group A have an average productivity of $15 per hour and that employers have a productivity test that is 100 percent accurate 1/3 of the time, but has no value 2/3 of the time. If a worker from group B took the same productivity test that was given to workers in group A, what is the best estimate of the VMP for this worker if his test score is $21 per hour? $18 $17 $21 $13