XVIII. AB Corp. entered into a contract with XY Corp. whereby the former agreed to construct the research and laboratory facilities of the latter. Under the terms of the contract, AB Corp. agreed to complete the facility in 18 months, at the total contract price of P10 million. XY Corp. paid 50% of the total contract price, the balance to be paid upon completion of the work. The work stated immediately, but AB Corp. later experienced work slippage because of labor unrest in his company. AB Corp.'s employees claimed that they are not being paid on time; hence, the work slowdown. As of the 17th month, work was only 45% completed. AB Corp. asked for extension of time, claiming that its labor problems is a case of fortuitous event, but this was denied by XY Corp. When it became certain that the contruction could not be finished on time, XY Corp. sent written notice cancelling the contract, and requiring AB Corp. to immediately vacate the premises. Can the labor unrest be considered a fortuitous event? (1%) Can XY Corp. unilaterrally and immediately cancel the contract? (2%) Must AB Corp. return the 50% downpayment? (2%)