Newton's laws of motion — practice question

Block $A$ has mass $80\,\text{kg}$ and is joined by a light, inextensible rope to block $B$, which has mass $40\,\text{kg}$. The rope between the blocks is taut and runs parallel to the line of greatest slope of a plane that is inclined at $20^\circ$ to the horizontal. A force of magnitude $500\,\text{N}$ acting at an angle of $15^\circ$ above that same line of greatest slope is applied to $A$ (see diagram). The blocks move up the plane, there is a resistance force of $50\,\text{N}$ on $B$, and there is no resistance force on $A$.