A bag contains 3 red and 4 black balls and another bag has 4 red and 2 black balls. One bag is selected, each of the two bags being equally likely to be selected. From the selected bag, a ball is drawn, each ball is the bag being equally likely to be drawn. Let `E_1` be the event: 'the first bag is selected , `E_2`, the event the second bag is selected and `E_3` , the event: 'a red balls is drawn. find `P(E_1),P(E_2),P(E_3//E_1) and (E_3//E_2)`.