(a) What is the probability David will host a group of at least 4 tourists? Show your work.

(b) What is the standard deviation of Danny's Jeep Tours? Show your work.

(c) How many TOTAL passengers can both David and Danny expect on any given day? Show your work.

Danny and David both give tours of San Francisco in Jeeps, but they have separate companies. Below is the probability distribution for David and Danny's Jeep Tours:

David:

Danny:

# Passengers (x)

2 3 4 5 6

Probability P(x) 0.15 0.25 0.35 0.20 0.05

# Passengers (x)

2 3 4 5

Probability P(x) 0.30 0.40 0.20 0.10

(a) What is the probability David will host a group of at least 4 tourists? Show your work.

(b) What is the standard deviation of Danny's Jeep Tours? Show your work.

(c) How many TOTAL passengers can both David and Danny expect on any given day? Show your work.

(d) Suppose you were taking the difference of Danny's Passengers minus David's passengers. Explain why you would add their standard deviations rather than subtract them.