/**
 * Estimates the bitterness of the beer based on a hop addition as
 * International Bittering Units. This is a estimate of bitterness not an
 * actual measure and the hop addition may yield more or less bitterness
 * than this calculation shows.
 * @param {number} alphaAcids alpha acids as a percentage for this hop addition
 * @param {number} boilTime time in minutes that this hop will be in the boil.
 * for example, a value of 60 means the hops will be in for the entirety of a
 * 60minute boil.
 * @param {number} weight weight in ounces
 * @param {number} volume volume of boil in gallons
 * @returns {number} positive integer of the international bittering units
 * calculation from a single hop addition
 */
export default function internationalBitteringUnits(alphaAcids: number, boilTime: number, weight: number, volume: number): number;