5.3 WNDS: 5.6: WinXP 5.1.2600 (Service Pack 2) [5.6.0.20040220] SntF C1100083162490D1100083284182D1100083579771D1100083732393 S9912 4 ~/x R(x, a) ~/x R(b, x) R(c, d) ;Conclusion R(a, b)