A certain elastic conducting material is stretched into a circular...

According to the Faraday's law of electromagnetic induction, the emf induced in a conducting loop is given by, $e = - \dfrac{d ϕ}{d t}$, here, $t$ is time and $ϕ = BA$ is magnetic flux.

Here, $e = \left|\dfrac{d ϕ}{d t}\right| = \dfrac{d \left(BA\right)}{d t} = B\dfrac{d \left(\pi{r}^{2}\right)}{d t}$

$= B\pi\left(2r\dfrac{d r}{d t}\right) = 2 \times \pi \times 0 . 1 \times 0 . 8 \times 2 \times {10}^{- 2}$

$\approx 10mV$ (rounded off)