V[m] = ((X1[2]-X1[1])*((Y1[3]-Y1[1])*(Z1[4]-Z1[1])-(Y1[4]-Y1[1])*(Z1[3]-Z1[1]))
    				+(X1[3]-X1[1])*((Y1[4]-Y1[1])*(Z1[2]-Z1[1])-(Y1[2]-Y1[1])*(Z1[4]-Z1[1]))
    				+(X1[4]-X1[1])*((Y1[2]-Y1[1])*(Z1[3]-Z1[1])-(Y1[3]-Y1[1])*(Z1[2]-Z1[1])))/6;