a.) Smith and Co. sold an equipment to the defendant Ben for P200,000 payable in quarterly installments of P20,000 each. The equipment was made security for the debt. Shortly after delivery to Ben, the equipment and the money for its quarterly payment were both lost in a fire which completely demolished the company's building. Is the buyer still liable? Why? If yes, when should he pay? Give the rights of the creditor.

b. Justin, Lyka, Apple and Pat borrowed money from Jessica. The contract stipulated a solidary one, but the debtors were bound under different terms and conditions. Jessica brought an action to recover from Justin whose obligation was already due. Justin claims that he cannot made to pay because of the obligations incurred by his solidary Co-debtors were not yet due. In a solidary obligation wherein the debtors are bound by different terms and conditions, may the creditor sue one of them?