This year I'll have 180 hours free during which I can play video games or watch movies, each movie lasts 2 hours, and I'll be able to play each video game for 20 hours , I have $600,each moves costs $10, and each game costs $40.

(a) If I make 3 new friends every time I get a new video game, and 1 new friend every time watch a movie, how many movies should I watch this year to maximize the number of new friends I make?