What would Mega Mawile's base attack be if it didn't have Huge Power?

Question

If Mega Mawile could still reach the same attack stat of 678 without Huge Power, how high would its base attack have to be?

EDIT: Include the formula used to calculate it.

Answer 1

Base stat is defined by the following formula for Attack, Defense, Speed, S Defense, S Attack, for a boosting Nature:

[(678/1.1) - (252/4) - 31 - 5]/2
[616 - 63 - 31 - 5]/2
517 / 2
= Base 259 Attack