Agroup os 29 friends gets together to play a sport. first, people must be divided into teams. each team has to have exactly 4 players, and no one can be on more than one team . how many teams can they make ? (it is possible that not everyone can be on a team.)

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?