a
$Young's\,modulus\,Y = \frac{F}{A}/\frac{{\Delta \ell }}{\ell }$
$Y = \frac{{Fl}}{{\pi {r^2}\Delta l}}$
$Given,\,radius = 5mm,forceF = 50\pi KN,$
$\frac{\ell }{{\Delta \ell }} = 0.01\,mm$
$\therefore \,Y = \frac{F}{{\pi {r^2}}}\frac{\ell }{{\Delta \ell }} = 2 \times {10^{14}}N/{m^2}.$