Answer: the answer is 1/5.
Explanation:
\frac{number \: of \: favorable \: outcomes}{total \: outcomes} \\ = \frac{number \: of \: ways \: where \: mum \: is \: at \: the \: front \: of \: the \: line}{total \: number \: of \: ways} \\ = \frac{1c1 ×4! }{5!} \\ = \frac{24}{120} \\ = \frac{1}{5}
Therefore the answer is 1/5.