Passage: Ammonium perchlorate ("AP") is an inorganic compound with the formula NH4ClO4.  It is a colorless or white solid that is soluble in water. It is a powerful oxidizer. Combined with a fuel, it can be used as a rocket propellant.  Its instability has involved it in a number of accidents, such as the PEPCON disaster.

Question: What is the formula of the inorganic compound ammonium perchlorate?
NH4ClO4