How can we define interdependent "sets" in GAMS code?

[kh_farajimahyari]

j={1,2,3,4}

i(j=1)={A,B} i(j=2)={C,D} i(j=3)={E,G,H,L} i(j=4)={M,N}
k(j=1)={K1,K2} k(j=2)={T1,T2,T3} k(j=3)={A1,A2} k(j=4)={B1,B2}

Fi,j,k=Alfai,j,k*Wi,j,k