TOKYO, Oct 21 (Reuters) - The president of Toyota Motor Corp said on Tuesday that while it was difficult to say what dollar-yen rate was appropriate, somewhere between 110 to 120 yen was reasonable when comparing labour costs between Japan and the United States. "This is very difficult to say, but when I think of the labour costs in Kentucky, where I oversaw the plant years ago, somewhere between 110 and 120 yen to the dollar is a good balance," Fujio Cho said at an auto industry conference