Kelsie works at a bicycle shop as a salesperson. she records the number of bicycles she sells daily. here is the probability distribution of b = the number of bicycles kelsie sells on a randomly selected day, and t the time she spends filling out daily sales reports. 2 b = # of bicycles sold t = time (minutes) probability 40 20 10 0.05 0.15 0.50 0.30

a) calculate e(b)
b) calculate the mean time she spends filling out daily reports.
c) calculate the standard deviation for both random variables.