Consider the polynomial \( P(x) = x^3 - 6x^2 + 11x - 6 \). Let \( r, s, t \) be the roots of \( P(x) \). Compute the sum of the squares of the roots, \( r^2 + s^2 + t^2 \). Let's think step by step and output the final answer within \boxed{}.
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