28.设命题ppp:实数xxx满足2<x⩽32<x\leqslant 32<x⩽3,命题qqq:实数xxx满足a<x<3aa<x<3aa<x<3a,其中a>0a>0a>0.若ppp是qqq的充分不必要条件,求实数aaa的取值范围.