Answer:
Increase
Explanation:
In putting the question into a better perspective let us assume that the US importer buys goods from Mexico every year to the Tune of 1,000,000 Mexican Pesos.
The expected exchange rate  on 1/1/X1=$0.1000*(1+2.5%)/(1+18%)
The expected exchange rate  on 1/1/X1=$0.086864407
Amount paid based on expected exchange rate=1,000,000*$0.086864407
Amount paid based on expected exchange rate=$86,864.41
Amount paid based on actual exchange=1,000,000*$0.085
Amount paid based on actual exchange=$85,000
The above means that the US importer paid a lesser amount($85000) than it should have paid, hence, its net cash flow would increase due to a reduction in payment