Two rabbits land on deserted Salt Island; they breed, and the number of rabbits on the island doubles every 4 weeks. Two other rabbits arrive on deserted Pepper Island; these rabbits triple every 4 weeks. At the end of the 12 weeks, one python arrives on each island. As each python grows, the number of rabbits it can eat each week doubles. The first week, each eats 1 rabbit, the second week, 2, and so forth. How long will it take the python to wipe out the rabbits on each island?