## is this a correct mathematical solution??

question:
http://i40.tinypic.com/2hwcswm.gif

solution:
$
\sigma=\frac{7.5\mu c}{14}=0.53571428571428571428571428571429\mu c\\
$

$
14=2\pi r\\
$

$
r=\frac{14}{\pi}\\
$

$
dq=\sigma r d\theta \\
$

$
k\sigma r\int_{0}^{\pi}d\theta=k\sigma r (\pi-0)=...
$

is it a correct solution?