reserve T, X, Y for Subset of MC-wff;
reserve p, q, r, s for Element of MC-wff;

theorem Th49:
  ( p => q ) => (( s '&' p ) => ( s '&' q )) in IPC-Taut
proof
  set P = p => q, Q = p '&' s, S = s '&' q, T = s '&' p;
A1: P => (Q => S) in IPC-Taut by Th48;
A2: T => Q in IPC-Taut by Th46;
  (P => (Q => S)) => ((T => Q) => (P => (T => S))) in IPC-Taut by Th27;
  then (T => Q) => (P => (T => S)) in IPC-Taut by A1,Def14;
  hence thesis by A2,Def14;
end;
