Dr. Jon planned to reward his class with candy. He surveyed every 4th student that entered the class to find out which candy he should buy. Was this random or biased sampling?

Sarah took the advertising department from her company on a round trip to meet with a potential client. including sarah a total of 11 people took the trip. she was able to purchase coach tickets for $280 and first class tickets for $1280. she used her total budget for airfare for the trip, which was $6080. how many first class tickets did she buy? how many coach tickets did she buy?