A vaccine for desensitizing patients to bee stings is to be packed with three vials in each box. Each vial is checked for strength before packing. The probability that a vial meets specifications is .9. Let X denote the number of vials that must be checked to fill a box. Find the density for X and its mean and variance. Would you be surprised if seven or more vials have to be tested to find three that meet specifications? Explain, based on the probability of this occurrence.