a
(a) Speed of sound in a stretched string $v = \sqrt {\frac{T}{\mu }} $…$(i)$
Where $T$ is the tension in the string and $\mu $ is mass per unit length.
According to Hooke’s law, $F \propto x$ $T \propto x$…$(ii)$
From $(i)$ and $(ii)$ $v \propto \sqrt x $ $\Rightarrow$ $v' = \sqrt {1.5} \;v = 1.22\;v$