Force F = (3.0 N) + (-9.0 N) acts on a pebble with position vector r = (1.00 m) + (-1.6 m) , relative to the origin.
(a) What is the resulting torque acting on the pebble about the origin?
(b) What is the resulting torque acting on the pebble about a point with coordinates (5.0 m, -4.0 m, -1.0 m)?