Asurvey of mba students reveals that among gmat scorers above 650, 52% took a preparatory course, whereas among gmat scorers of < 650 only 23% took a preparatory course. an applicant to an mba program has determined that she needs a score of more than 650 to get into a certain mba program, but she feels that her probability of getting the desired score is 30%. she is considering taking a preparatory course that cost $500. she is willing to do so only if her probability of achieving 650 or more becomes higher than 50%. calculate this probability.