Photosynthetic rate calculation
Using the general case equation
$$\frac{P_1V_1 }{T_1} = \frac{P_2 V_2} {T_2}$$
and given that pressure is constant at $\pu{1  atm}$ in your experiment, the equation simplifies to
$$\frac{V_1 }{T_1} = \frac{ V_2} {T_2}$$
We know $V_1=\pu{960 \mu L}$ and it appears that the experiment is being run at $\pu{(273+23)K}$, so we need to calculate what the volume ($V_2$) would be at standard T ($\pu{273 K}$).  This is given by
$$V_2 = \frac{V_1 T_2}{T_1}$$
if we next divide $V_2$ by $\pu{22.423E6 \mu~L}$, we now know how many moles of $\ce{O2}$ we have.