YES(?,O(n^2)) Problem: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),s(y)) -> s(y) s(+(0(),y)) -> s(y) Proof: Matrix Interpretation Processor: dimension: 2 interpretation: [8] [s](x0) = x0 + [1], [1 1] [8] [+](x0, x1) = x0 + [0 1]x1 + [0], [7] [0] = [9] orientation: [24] +(x,0()) = x + [9 ] >= x = x [1 1] [17] [1 1] [16] +(x,s(y)) = x + [0 1]y + [1 ] >= x + [0 1]y + [1 ] = s(+(x,y)) [1 1] [24] [8] +(0(),s(y)) = [0 1]y + [10] >= y + [1] = s(y) [1 1] [23] [8] s(+(0(),y)) = [0 1]y + [10] >= y + [1] = s(y) problem: Qed