The number of structural and configurational isomers of a bromo compound ${\mathrm{C}}_5{\mathrm{H}}_9\mathrm{Br}$, formed by the addition of HBr to 2-pentyne respectively, are

The structural isomers are ${\mathrm{CH}}_3\mathrm{CH}=\mathrm{CBr}-{\mathrm{CH}}_2-{\mathrm{CH}}_3$ and ${\mathrm{CH}}_3\mathrm{CBr}=\mathrm{CH}-{\mathrm{CH}}_2-{\mathrm{CH}}_3$There will be four configurational isomers, cis- and trans-isomers of each of the above two compounds.