The postal service of St. Vincent, an island in the West Indies, obtains a significant portion of its revenues from sales of special souvenir sheets to stamp collectors. The postal service purchases the souvenir sheets from a supplier for $0.80 each. St. Vincent has been selling the souvenir sheets for $8.00 each and sells about 80,000 units.

To test the market, the postal service recently priced a new souvenir sheet at $7.00 and sales increased to 94,400 units. The fixed expenses are $ 350,000 per year.

What percentage increase in unit sales to happen at the lower price of $7.00 to provide the same profit being earned a price of $8.00?