Answer
The period of the oscillation is 0.75 seconds.
Work Step by Step
If the mass is at rest on the spring when the spring is stretched $x = 14~cm$, we can find an expression for $\frac{m}{k}$.
$mg = kx$
$\frac{m}{k} = \frac{x}{g}$
We can find the period $T$ of the oscillations. as:
$T = 2\pi~\sqrt{\frac{m}{k}}$
$T = 2\pi~\sqrt{\frac{x}{g}}$
$T = 2\pi~\sqrt{\frac{0.14~m}{9.80~m/s^2}}$
$T = 0.75~s$
The period of the oscillation is 0.75 seconds.