A box with mass $8.0\,\text{kg}$ is at rest on a rough horizontal surface. A string is fixed to the box, runs over a smooth pulley, and holds a $2.0\,\text{kg}$ mass on the opposite side. Once the box is let go, a frictional force of $6.0\,\text{N}$ acts on it. What is the acceleration of the box?
- A$1.4\,\text{m s}^{-2}$
- B$1.7\,\text{m s}^{-2}$
- C$2.0\,\text{m s}^{-2}$
- D$2.5\,\text{m s}^{-2}$