Since, tertiary `(3^(@))` carbocation is far more stable than the primary `(1^(@))` carbocastion, the major product obtained will be in the case (a).
`CH_(3)-underset(CH_(3))underset(|)(C)=CH_(2)+HBrrarrCH_(3)-underset(CH_(3))underset(|)overset(Br)overset(|)(C)-CH_(3)`