Zero. e raised to negative infinity is 1/e raised to infinity. That's 1/infinity which is zero.
The Great Ape (大猿, Ōzaru, lit, "Great Monkey") transformation is a transformation inborn to all Saiyans in the Saiyan race.
It's technically cannon only to the anime and only fully canon to the old anime continuity. The only reason why people say GT Isn't at all cannon is because there's no manga for it the dragon ball ended with the end of Z/buu arc. parts of it still can exist while other parts contradicts the current continuity.