The period of oscillation of a simple pendulum is $T = 2\pi\sqrt{L/g}$. Measured value of $L$ is $20.0\,\text{cm}$ known to $1\,\text{mm}$ accuracy and time for $100$ oscillations of the pendulum is found to be $90\,\text{s}$ using a wrist watch of $1\,\text{s}$ resolution. The accuracy in the determination of $g$ is: