Question: Timber! A lumber company wants to estimate the proportion of trees in a large forest that are ready to be cut down. They use an aerial map to divide the forest into 200 equal-sized rectangles. Then they choose a random sample of 20 rectangles and examine every tree that's in one of those rectangles.
(a) What is the name for this kind of sampling method?
(b) Give a possible reason why the lumber company chose this method.