A particle is acted on by two torques about the origin: r, has a magnitude of 2. 8 N-m and is directed in the positive direction of the x-axis, and r 2 has a magnitude of 5. 5 N-m and is directed in the negative direction of the y-axis. In unit-vector notation, find d ℓ/dt. where C is the angular momentum of the particle about the origin.