(a) Verify that this is a discrete probability distribution. This is a discrete probability distribution because the sum of the probabilities is 1 and each probability is between 0 and 1, inclusive. (0) Compute and interpret the mean of the random variable x. The mean is - activities. (Type an integer or a decimal. Do not round.) (d) Compute the standard deviation of the random variable x. The standard deviation is. activities. (Round to one decimal place as needed.) (9) What is the probability that a randomly selected student has a parent involved in three activities? The probability is . (Type an integer or a decimal. Do not round.) (f) What is the probability that a randomly selected student has a parent involved in three or four activities? The probability is - (Type an integer or a decimal. Do not round.)