Definition: In this task, you're given a question, along with a context passage. The passage will not have a direct answer to the question, but can include some information and a clue for the answer. Assuming you can only obtain information about one entity in the passage, your job is to determine whether information from the passage can be used to answer the question. Indicate your choice as `a` for Yes or `b` for No.
Input: Question: Which country designed the fighter planes that the Yugoslav Air Force used but were badly maintained? Passage:An important portion of the 1999 war between Yugoslavia and the NATO coalition involved combat between the Yugoslav Air Force, which was the predecessor of today's Serbian Air Force, and the opposing air forces of NATO. United States Air Force F-15s and F-16s flying mainly from Italian air force bases attacked the defending Yugoslav fighters—usually MiG-29s, which were in bad shape, due to lack of spare parts and maintenance. A total of six Yugoslav MiG-29s were shot down in 1999, of which three were shot down by USAF F-15s, one by a USAF F-16, and one by a RNAF F-16. One aircraft, according to a Serbian documentary, was hit by friendly fire from the ground. Another four were destroyed on the ground. During the course of the air war, Yugoslav anti-aircraft defenses downed a USAF F-16C and an F-117 Nighthawk, the first stealth aircraft to ever be shot down in combat.


b