/**
 * Profitability Index (PI) is an index that attempts to identify the relationship between the costs and benefits of a proposed project through the use of a ratio calculated.
 *
 * @see http://www.investopedia.com/terms/p/profitability.asp
 * @param rate
 * @param cfs
 * @returns
 */
export declare function PI(rate: number, cfs: number[]): number;