While Playing Monopoly, Andi Estimated the Probabilities of the Non-Zero

Essay

While playing Monopoly, Andi estimated the probabilities of the non-zero rents according to the following probability distribution: Consider the random variable x = dollar amount in rent collected in a Monopoly roll.
a) If the table above specifies the probability distribution of x, what is the mean of the random variable x?
b) If the probabilities are associated with the outcomes as in the table above, what is the standard deviation of the random variable x?