A brick with weight $20\ \text{N}$ is at rest on a sloping plane. Its weight has a $10\ \text{N}$ component acting parallel to the plane. The brick also has a frictional force of $4\ \text{N}$ acting on it. What is the acceleration of the brick down the plane? Assume that the acceleration of free fall $g$ is equal to $10\ \text{m s}^{-2}$.
- A$0.3\ \text{m s}^{-2}$
- B$0.8\ \text{m s}^{-2}$
- C$3.0\ \text{m s}^{-2}$
- D$8.0\ \text{m s}^{-2}$