On an IQ test, the mean score is 100 with a standard deviation of 15. Letting X represent a randomly selected IQ score, write an expression that describes the probability of a randomly selected IQ score being less than 85. An expression that describes the probability of a randomly selected IQ score being less than 85 is P (Be sure to use the variable x.) In testing light bulbs at a new plant, it was found that the bulbs lasted a mean of 1500 hours with a standard deviation of 40 hours. Letting t represent the number of hours a randomly selected light bulb lasts, write an expression that describes the probability of a randomly selected light bulb lasting between 1380 and 1540 hours. An expression that describes the probability of a randomly selected light bulb lasting between 1380 and 1540 hours is P (Be sure to use the variable t.)