Answer
$0.67KN$
Work Step by Step
We can find the required tension as
$\Sigma F_y=T-W=ma_c$
$\implies T=W+ma_c$
$T=mg+\frac{mv^2}{r}$
$T=m(g+\frac{v^2}{r})$
We plug in the known values to obtain:
$T=(63)(9.81+\frac{(2.4)^2}{6.9})$
$T=0.67KN$