Coursework Prolog

items([item(fork,20,2),
     item(spoon,50,5),
     item(knife,100,3),
     item(table,10,100)]).
firma(_,[],[]).
firma(N,[item(N,S,V)|T],[S,V|T1]):- write(S*V),firma(N,T,T1).
firma(N,[H|T],T1):-firma(N,T,T1).

?-write(" write item "),nl,read(N),items(L),write("The price of all "),
write(N),write("s is: " ),firma(N,L,L1),nl.