How many monobromination products (constitutional isomers only, stereoisomers not counted) can the alkane shown give on reaction with $\mathrm{Br}{}_2$/light?

The compound shown is 2-methylbutane. Replacing H at the two equivalent $\mathrm{CH}{}_3$ groups on C2, at C2-H, at the $\mathrm{CH}{}_2$, or at the terminal $\mathrm{CH}{}_3$ gives four different bromides: 1-bromo-3-methylbutane, 2-bromo-2-methylbutane, 2-bromo-3-methylbutane and 1-bromo-2-methylbutane.