Answer
Please see the work below.
Work Step by Step
According to law of conservation of energy
$\frac{1}{2}mv^2=\frac{1}{2}kx_{\circ}^2$
This simplifies to:
$k=\frac{mv^2}{x_{\circ}^2}$
We plug in the known values to obtain:
$k=\frac{1500(2400)^2}{(17)^2}=29.9M\frac{N}{m}$
