[tex]\bf \textit{area of a circle}\\\\
A=\pi r^2\quad
\begin{cases}
r=radius\\
-----\\
r=1.4
\end{cases}\implies A=\pi 1.4^2\implies A=\stackrel{m^2}{1.96\pi}
\\\\\\
\textit{now, decolam is }\stackrel{rupees}{50}~per~m^2\implies \stackrel{\textit{total cost}}{50\cdot 1.96\pi }[/tex]
