Three boys of class X, four boys of class XI, and five boys of class XII sit in a row. The total number of ways in which these boys can sit so that all the boys of same class sit together is equal to a. `(3!)^2(4!)(5!)` b. `(3!)(4!)^2(5!)` c. `(3!)(4!)(5!)` d. `(3!)(4!)(5!)^2`