person to believe in the existence of the contract or business relationship. Armendariz v. Mora, 553 S.W.2d 400, 405 (Tex.Civ.App. — El Paso 1977, writ ref'd n.r.e.); Frost National Bank v. Alamo National Bank, 421 S.W.2d 153, 156 (Tex.Civ.App. — San Antonio 1967, writ ref'd n.r.e.); Kelly v. Rozelle, 294 S.W. 699, 701 (Tex.Civ.App. — Austin 1927, writ dism'd). In answer to special issue number three, the jury found that Steinmetz Associates, Inc. knew or in the exercise of ordinary care should have known of the existence of a contract for the sale of Lot 15 between Larry Crow and Juanita Ramos and her children, the sellers.

"It is well settled that, if a plaintiff declares on an express contract, he cannot recover on an implied contract." Shelton et al. v. Lemmon et al. (Tex.Civ.App.) 268 S.W. 177, 178; Kelly et al. v. Rozelle (Tex.Civ.App.) 294 S.W. 699. The contract between Clark and Williams was bilateral and executory, granted rights and imposed duties and obligations on each party thereto.