Blue information is 'secured', red = possible alternatives. The red alternatives do not move the numbers in the two rightmost columns.
Blue 'b' + 'c' gives: 14 + 13 + 13 + 14 + 13 + 14 = 40 + 41 = 81 = 27 + 27 + 27 = 3 * 27 = 34
Blue 'a' gives: 16 + 12 + 9 + 15 + 46 + 15 = 113 = 37 + 76 = 28 + 24 + 61 = 52 + 61 = 28 + 85 = 16 + 21 + 61 + 15
Red 'b' + 'c' gives: 6 * 14 = 84 = 42 + 42 = 28 + 28 + 28 = 7 * 12
Red 'a' gives: 16 + 11 + 8 + 15 + 45 + 15 = 110 = 35 + 75 = 27 + 23 + 60 = 50 + 60 = 27 + 83 = 16 + 19 + 60 + 15