A light rod AC is 0.80m long and is pivoted at its mid-point O. A downward force of 10N acts at end A (left end). Another downward force of 8N acts at a point 0.20m to the right of O. Taking anticlockwise torque as positive, the net torque about O is
a) −2.4N m
b) +5.6N m
c) +2.4N m
d) +0.8N m