in the aforementioned gharar yasir; where the contract is "unilateral or charitable" (al tabarru'at) so that the other party to the contract is not exploited, such as a gift or bequest; where there is a "public need for the transaction or contract" (maslahah, for example in the Islamic finance instruments of bay' al salam and istisna`); where risk (ghurm) "inherent in productive economic activities".