R-1.4 A hollow circular post ABC (see figure) supports a = load Pi 16kN acting at the top. A second load P₂ is uniformly distributed around the cap plate at B. The diam eters and thicknesses of the upper and lower parts of the 12 mm, dc = 60 mm, post are d and inc = AB = 30 mm, AB 1 = BC 9 mm, respectively. The lower part of the post must have the same compressive stress as the upper part. The required magnitude of the load P, is approximately: (A) 18 kN (B) 22 kN (C) 28 kN (D) 46 kN TAB dAB dBC tpc