${\mathrm{E}}^{\circ }$ for ${\mathrm{F}}_2+2\mathrm{e}⟶2{\mathrm{F}}^{-}$ is $2.8 \mathrm{V}$, 

${\mathrm{E}}^{\circ }$ for $\frac{1}{2}{\mathrm{F}}_2+\mathrm{e}⟶{\mathrm{F}}^{-}$ is

Electrode potential data are given below.

${\mathrm{Fe}}^{3+}\left(\mathrm{aqueous}\right)+{\mathrm{e}}^{-}⟶{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right); {\mathrm{E}}^{\circ }=+0.77$

${\mathrm{Al}}^{3+}\left(\mathrm{aqueous}\right)+3{\mathrm{e}}^{-}⟶\mathrm{Al}\left(\mathrm{s}\right); {\mathrm{E}}^{\circ }=-1.66 \mathrm{V}$

${\mathrm{Br}}_2\left(\mathrm{aqueous}\right)+2{\mathrm{e}}^{-}⟶2{\mathrm{Br}}^{-}\left(\mathrm{aqueous}\right); {\mathrm{E}}^{\circ }=+1.08 \mathrm{V}$

Based one the data given above, reducing power of ${\mathrm{Fe}}^{2+}, \mathrm{Al}$ and ${\mathrm{Br}}^{-}$ will increase in the order:

Given standard electrode potentials:

${\mathrm{Fe}}^{3+}+3{\mathrm{e}}^{-}⟶\mathrm{Fe}; \mathrm{E}°=-0.036 \mathrm{volt}$

${\mathrm{Fe}}^{2+}+2{\mathrm{e}}^{-}⟶\mathrm{Fe}; \mathrm{E}°=-0.440 \mathrm{volt}$

The standard electrode potential $\mathrm{E}°$ for ${\mathrm{Fe}}^{3+}+{\mathrm{e}}^{-}⟶{\mathrm{Fe}}^{2+}$.

${\mathrm{Cu}}^{+}+{\mathrm{e}}^{-}⟶\mathrm{Cu}, \mathrm{E}°={\mathrm{x}}_1 \mathrm{volt}$

${\mathrm{Cu}}^{2+}+2{\mathrm{e}}^{-}⟶\mathrm{Cu}, \mathrm{E}°={\mathrm{x}}_2 \mathrm{volt}$

Then for ${\mathrm{Cu}}^{2+}+{\mathrm{e}}^{-}⟶{\mathrm{Cu}}^{+}$, $\mathrm{E}°\left(\mathrm{volt}\right)$ will be: