Leo's Fruit Stand has always stocked just one brand of apples: Gala. Gala apples cost Leo $0.11 each, and he sells them for $0.51. Leo is considering adding Rome apples to his stand. They will cost him $0.23 each and he plans to sell them for $0.49 each. Leo expects Rome apple volume to be half of Gala's previous volume of 2,400 per month. He also expects 32% of Rome volume to be taken from Gala volume.

What percentage sales decrease will Gala suffer as a result of the introduction of Rome apples to the stand?