Is this solution correct ? i didn't get the logic. can you explain the solution ?

The number of ways can 4 particles be distributed over various energy states such that two particles are in energy state Es, none in E2, one in Eg, one in E4 is (Answer should be an integer) Solution Distribution 2E +E +E, = 4E Now, no. of ways by which particle to be distributed -E. 4! =12 21011!1! E -E E So, W(4)= w4)=12