In this type of contract, the elements are not specifically written or expressed. In fact, this type of contract is used as a remedy in a situation when one party to the quasi-agreement received unjust enrichment resulting from not paying for a product or service rendered.
A Drupe is a single fleshy fruit with a hard stone which contains the single seed. This is a Cherry (Prunus avium). Other fruits of this type are: Apricot (Prunus armeniaca), Plum (Prunus x domestica), Coconut (Cocos nucifera), Olive (Olea europaea), Peach (Prunus persica), Sloe (Prunus spinosa).
E.g. peach, plum, nectarine, apricot, cherry, olive, mango and almond. Some botanists also include the fruits of walnuts, pecans, date palms, macadamia nuts, pistachio nuts, tung oil and kukui nuts as drupes because of their outer, green, fleshy husk and stony, seed-bearing endocarp.