Sentence:  This sum spent for foreign economic aid , the peace corps , food for peace , or any other program to solve the problems of the underdeveloped countries would <WSD>be</WSD> an investment that would pay off in world peace , increased world trade , and prosperity for every country on the globe . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)