The answer would be 45 weeks, since you do 530-80 since that is the part the parents will foot, which will be 450 left. Then you do that divided by 10 since you plan to save 10 dollars a week and therefore are left with 45 weeks.
C, planes are more likely to take off on time. .72 as a percent is 72%. Hence, a relatively high probability that the planes will take of on time.
If you showed me the diagram I could give you an answer.
