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great point Ozmba, one thing i am not sure of, is what is the reason behind 1-y instead of y-1. If y-1 =0 then y=1. therefore y is not less than 1, it must be one to make it equal.

My way gives a wrong answer which luckily is not in the answer choices, and your way gives the right answer. I am just asking you, in case i will see it during the real thing.

When in doubt of the shortcuts, take the long way. Just plug the numbers and solve. Ozmba has done it the quickest way. If you don't understand why it needs to be (1-y) instead of (y-1), just plug numbers and you will see how it works.