A large firm has 85% of its service calls made by a contractor, and 10 of these

Question:

A large firm has 85% of its service calls made by a contractor, and 10 of these calls result in customer complaints. The other 15% of the service calls are made by their own employees, and these calls have a 5% complaint rate. Find the
(a) Probability of receiving a complaint.
(b) Probability that the complaint was from a customer serviced by the contractor.