If you assume you have N eggs hatch from a clutch then your percent chance of producing a Lucy is (1-.75^N)*100

1 egg gives 25% chance
2 eggs give 46.8% chance
4 eggs give 68.4% chance
6 eggs give 82.2% chance
8 eggs give 90% chance
an infinite amount of eggs produces a Lucy with 100% chance

JonV