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1. If c = (m, n, 1) is perpendicular to both a = (5,1, -2) and b = (3, -3,6), find m and n. [TH - 5] 2. ABCD is a quadrilateral where W, X, Y, and Z are respectively the midpoints of AB, BC, CD, and AD respectively. Prove that WXYZ is a parallelogram. [TH - 5]