a=-1,b=1,c=-1/2
-1/3a^2bc^2×4ab^2c
=-4/3*a^3b^3c^3
=-4/3(abc)^3
=-4/3[(-1)*1*(-1/2)]^3
=-4/3*(1/2)^3
=-4/3*1/8
=-1/6