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Number theory Difficulty 3.0 AMC 10/12 Find the answer United Kingdom

Four different positive integers $p, q, r, s$ satisfy the equation $(9-p)(9-q)(9-r)(9-s) = 9$ . What is the value of $p+q+r+s$ ?

(A) $20$ (B) $24$ (C) $28$ (D) $32$ (E) $36$

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