If x and y are distinct positive integers and x+y

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If x and y are distinct positive integers and x+y is even, what is the remainder when (x+y)^a is divided by 10, where a is a positive integer?

(1) Units digit of y is 6.
(2) (xy)^a is divisible by 10.

I know each statement alone is not sufficient. But I don't know how to use both together. Experts, can you explain this DS question to me?
Source: — Data Sufficiency |