Which Is the Best Example of Someone Using a Heuristic

Which is the best example of someone using a heuristic in problem solving?

A) Susan wants to know how long it will take her to drive from Edmonton to Calgary.She knows that the distance is 300 kilometres, and she figures she will average 100 kilometres an hour with stops, so she predicts the trip will take 3 hours.
B) Vinnie has a round hot tub that is six feet in diameter; he wants to build a top to cover it.He remembers the formula for calculating the area of a circle and works out how many feet of lumber he needs.
C) Mark wants to buy a computer.He compares prices at different computer stores and buys the one that is least expensive.
D) Marion cannot think of a plot for the short story she needs to write.She breaks her task into smaller pieces: First she will decide who her main character will be, then she will think of a conflict for that character to experience, and finally she will identify a reasonable resolution for that conflict.