Which situation best illustrates a marginal change?
a. Banff, which usually receives 600 cm of snow per year, received 620cm last year.
b. Nancy retires and takes a part-time job. She was working 40 hours per week, but now works 10 hours per week.
c. Adam moved from Edmonton to Toronto and now pays 40% more for rent than before.
d. Provincial University has announced that due to provincial budget deficits, tuition must rise by 25% next year.