Jason operates an interior design business and relies on contractors in a variety of industries to complete the work. However, some clients just want him to design, and they'll do the work themselves. His last job was like that; he spent 17 hours designing an updated kitchen, bath, and entryway for a client. For these design-only jobs, he bills clients at a flat rate of $36 per hour that covers both his labor and overhead costs. His next client has a complex job that requires the use of contractors. This time, Jason breaks the job into key activities, using specific predetermined rates to create the bid: $180 per room designed, $17 per hour (for Jason's time), and $170 per change order (if the client makes additional changes after the design is set). All direct costs will be billed directly by the supplier or contractor. Jason does not include a separate overhead rate in these more complex jobs. The client's more complex job includes the following work: a remodeled kitchen, two remodeled bathrooms, and a contractor to pull together all of the pieces (Jason estimates 17 hours of his own time to coordinate with the contractor). (a1) Jason billed $612 to his design-only client for the 17-hour project initially described, using his flat rate of $36 per hour. Since the $36 rate covers both labor and overhead, how much does he estimate for his hourly overhead rate? Overhead hourly rate $