A stepped shaft ABC, 1 m long made of steel is of diameter 20 mm from A to B = 0.5 m, 40 mm from B to C =0.5 m. It is subjected to twisting moments 0.4 kNm (cw) at A. 0.8 kN-m (ccw) at band 0.4 kN-m (cw) at C. If G = 84 kN/mm2 determine angular twist between A to C.