Answer
$7.5\times10^{-21}s $
Work Step by Step
Estimate the lifetime by using equation 28–2.
$$\Delta E \approx \frac{\hbar}{\Delta t}$$
$$\Delta t \approx \frac{\hbar}{\Delta E}$$
$$=\frac{1.055\times 10^{-34}J \cdot s}{88\times10^3eV}\frac{1eV}{1.60\times10^{-19}J}$$
$$ \approx 7.5\times10^{-21}s $$