Kendra needs help on her math homework and decides to call one of her friends- Amber, Bob, or Carol. Kendra knows that Amber is on the phone 30% of the time, Bob is on the phone 20% of the time, and Carol is on the phone 25% of the time.
a. If the three friends' phone usage is independent, make a Venn diagram of the situation.
b. What is the probability that all three of her friends will be on the phone when she calls?
c. What is the probability that none of her friends will be on the phone when she calls?