:o It's been awhile I can't remember how to do this

ONE BLUE BALL AND FOUR RED BALLS ARE PLACED IN A BOX. TWO RED BALL AND THREE BLUE BALLS ARE PLACED IN A SECOND BOX. A BOX IS CHOSEN AT RANDOM, AND A BALL IS SELECTED FROM IT. THE PROBABILITY OF CHOOSING THE FIRST BOX IS 3/8. FIND THE PROBABILITY THAT THE BALL IS FROM THE SECOND BOX, GIVEN THAT IT IS RED.

Please help!!! I need to jog my memory