A)
from google:
With a degree in mechanical engineering students can get an Air Force assignment as an aeronautical engineer, astronautical engineer, civil engineer, mechanical engineer or project engineer. The mechanical engineering degree also satisfies the educational requirements for Air Force test pilot, flight test combat systems officer and flight test engineer duties. Additional specialties are scientific analyst and acquisition project officer. Successful completion of this degree may qualify you for assignment in the developmental mechanical engineer career field.
b) low availability of engineer-specific jobs. Any job as a USAF officer will help get a job after serving.
c) These jobs are NOT guaranteed, you can not be promised any particular job. You agree to service first, and everything else comes second.