Answer
$a_0 = 5.29\times 10^{-11}~m$
Work Step by Step
We can calculate the value of $a_0$:
$a_0 = \frac{\hbar^2}{m_e~k~e^2}$
$a_0 = \frac{(1.0546\times 10^{-34}~J~s)^2}{(9.1\times 10^{-31}~kg)(9.0\times 10^9~N~m^2/C^2)(1.6\times 10^{-19}~C)^2}$
$a_0 = 5.29\times 10^{-11}~m$
