(a) Sine rule: \(\sin R/50=\sin140^\circ/100\Rightarrow R=\sin^{-1}(\tfrac12\sin140^\circ)\approx18.7^\circ\). The obtuse alternative is impossible with Q already 140°. (b) Reverse bearing R to Q = 280°. From the diagram, RP is 18.7° anticlockwise from RQ: \(280-18.7=261.3^\circ\), approximately 261°.