c
અહી \(\mathop r\limits^ \to  \,\, = \,\,5\hat i\,\, - \,\,3\hat j\,\, + \;\,0\hat k\) અને  \(\mathop F\limits^ \to  \,\, = \,\,4\hat i\,\, - \,\,10\hat j\,\, + \;\,0\hat k\)

\(\therefore \,\,\mathop \tau \limits^ \to  \,\, = \,\,\mathop r\limits^ \to  \,\, \times \,\,\mathop F\limits^ \to  \,\, = \,\,\left| {\left. {\begin{array}{*{20}{c}}
{\hat i}&{\hat j}&{\hat k}\\
5&{ - 3}&0\\
4&{ - 10}&0
\end{array}} \right|} \right.\,\)

\( = \,\,\hat i\,\left( {0\,\, - \,\,0} \right)\,\, - \,\,\hat j\,\left( {0\,\, - \,\,0} \right)\,\, + \;\,k\left( { - 50\,\, + \;\,12} \right)\,\, = \,\, - 38\hat k\)