A company has two plants which manufacture scooters.Plant I manufactures 80% of the scooters while Plant II manufactures 20% of the scooters.At plant I ,85 out of 100 scooters are rated as being of standard quality,while at Plant II only 65 out of 100 scooters are rated as being of standard quality.If a scooter is of standard quality,what is the probability that it came from Plant I?