a
\(\begin{array}{l}
\overrightarrow F = - 5\hat i + 9\cos {60^ \circ }\hat i + 9\sin {60^ \circ }\hat j - 3\hat j\\
\,\,\,\,\, = \,\, - 5\hat i + \frac{9}{2}\hat i + \frac{{9\sqrt 3 }}{2}\hat j - 3\hat j\\
\,\,\,\,\, = - \frac{{\hat i}}{2} + \left( {\frac{{9\sqrt 3 }}{2} - 3} \right)\hat j\\
\overrightarrow s = - 3\hat i.\\
W = \overrightarrow F \overrightarrow s = \left[ { - \frac{{\hat i}}{2} + \left( {\frac{{9\sqrt 3 }}{2} - 3} \right)\hat j} \right].\left( { - 3\hat i} \right)\\
\,\,\,\,\,\,\,\,\,\,\,\, = 1.5\,J.
\end{array}\)