# Square the Square #4th power

If $$n$$ is a perfect square, and $${ n }^{ 2 }\equiv k(mod\quad 10)$$ what is the sum of all the possible values of $$k$$ and the number of values of $$k$$

Example: Suppose $$k$$ has $$2$$ values, $$3$$ and $$4$$. Then the answer would be $$2+3+4=9$$

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