Sarah took the advertising department from her company on a round trip to meet with a potential client. Including Sarah a total of 15 people took the trip. She was able to purchase coach tickets for ​$320 and first class tickets for ​$1,260. She used her total budget for airfare for the​ trip, which was ​$11,380. How many first class tickets did she​ buy? How many coach tickets did she​ buy?