Newton's laws of motion — practice question

A block $A$ with mass $2\text{ kg}$ and a particle $B$ with mass $0.5\text{ kg}$ are joined by a light inextensible string that is tilted at $15^\circ$ to the horizontal. They are dragged over a horizontal surface with acceleration $1.2\text{ m s}^{-2}$ by a force of magnitude $6\text{ N}$ applied to $A$, which acts at $20^\circ$ above the horizontal, as illustrated in the diagram. The string and the force on $A$ lie in the same vertical plane. The contact between $B$ and the surface is smooth, whereas the contact between $A$ and the surface is rough.