The amount spent per week on food at Jim's student flat is $80 with probability 0.2, $90 with probability 0.4, $100 with probability 0.3 and $105 with probability 0.1. Simulate the amount spent on food for a semester(12 wekks) and estimate the probability that:

a) they spend more than $100 in each of the first two weeks of a semester
b) they spend more than $80 in at least 7 weeks of a semester
c) they spend an average of less than $94 per week in a semester