The U.S. bi-lateral real exchange rate with Mexico is defined as S/(P_MEX/P_US), where S is the nominal exchange rate in pesos per U.S. dollar (pesos/$), P_MEX is the Mexican consumer price level, and P_US is the U.S. consumer price level. What would the effect on U.S. competitiveness be, other things being equal, of:

1. A fall in the peso relative to the dollar?
2. A rise in Mexican inflation?
3. A rise in U.S. inflation?
4. A simultaneous rise in the peso and decline in Mexican inflation of about the same amount (say, 10%)?