>>301
Total[
Sum[(n1+n2+n3+n4)Multinomial[n1,n2,n3,n4-1] Multinomial[40-n1,30-n2,20-n3,10-n4],{n1,1,40},{n2,1,30},{n3,1,20},{n4,1, 1}]+
Sum[(n1+n2+n3+n4)Multinomial[n1,n2,n3-1,n4] Multinomial[40-n1,30-n2,20-n3,10-n4],{n1,1,40},{n2,1,30},{n3,1, 1},{n4,1,10}]+
Sum[(n1+n2+n3+n4)Multinomial[n1,n2-1,n3,n4] Multinomial[40-n1,30-n2,20-n3,10-n4],{n1,1,40},{n2,1, 1},{n3,1,20},{n4,1,10}]+
Sum[(n1+n2+n3+n4)Multinomial[n1-1,n2,n3,n4] Multinomial[40-n1,30-n2,20-n3,10-n4],{n1,1, 1},{n2,1,30},{n3,1,20},{n4,1,10}]
]/Multinomial[40,30,20,10]
=15696077/1378377=11.3873613677535...