On the planet ZOG, colored coins are used for money. Suppose 12 white, 9 red, 8 yellow, 4 blue and 0 green coins can be exchanged for 2 white, 1 red, 0 yellow, 1 blue and 1 green coin. Also suppose 1 green = n blue, 1 blue = n yellow, 1 yellow = n red, and 1 red = n white. What is the whole number rate of exchange for these coins? Is only one exchange rate possible?