X, owner of a mining claim, appointed as attorney-in-fact to enter into a contract with any individual or juridical person for the exploration and development of said claim on a royalty basis. Y himself embarked upon the exploitation of the claim. Subsequently, X revoked the authority to Y who assented thereto subject to certain conditions. As a result, a document was executed wherein T transferred to X all of Y's rights and interests over the "24 tons of iron ore, more or less" that Y had already extracted from the mineral claims in consideration of the sum of P75,000.00, P10,000.00 of which was paid upon the signing of the agreement, and "the balance of P65,000.00 will be paid from and out of the first letter of credit covering the first shipment of iron ores and of the first amount derived from the local sale of iron ore "from said claims.To secure the payment of the balance, X executed in favor of Y a surety bond. No sale of approximately 24,000 tons of iron ore had been made nor had the balance of P65,000.00 been paid to Y.Is the shipment or the local sale of the iron ore a condition precedent (or suspensive condition) to the payment of the balance, or only a suspensive period or term?