A purchasing agent placed a rush order for a particular raw material with two different suppliers, A and B. If neither order arrives in four days the production process must be shut down until at least one of the orders arrives. The probability that supplier A can deliver the material in four days is 0.55. The probability that supplier B can deliver the material in four days is 0.35.

a. What is the probability that both suppliers deliver the material in four days? Because two separate suppliers are involved, assume independence.

b. What is the probability that at least one supplier delivers the material in four days?

c. What is the probability the production process is shut down in four days because of a shortage in raw material (that is, both orders are late)?