Last year, James Hunt went on vacation to Mexico City. At the time, he exchanged his dollars at an exchange rate of 15 Pesos (MXN) to the dollar (USD). This year, as he prepares to take another vacation in Mexico, the dollar is worth 18.75 Pesos.

If inflation, during this one-year period, was 2% in the US, and 18% in Mexico, by how much (%) will James' purchasing power increase when he returns to Mexico on vacation, after exchanging his dollars at 18.75 Pesos?