A and B and C executed a promissory note binding themselves to pay P9r000 to X, Y and.Z. The note is now due and demandable. (a) Can the creditors proceed against A alone for payment of the entire obligation? Why? (b) Can X alone proceed against A, B and C for pa5rment of the entire obligation? Why? (c) Suppose that X proceeds against A alone for payment, how much can he collect? Why? (d) Suppose that C is insolvent, can A and B be held liable for his share in the obligation? Why? (e) Suppose that the obligation was about to prescribe, but X wrote a letter to A demanding for payment of the entire debt, will this have the effect of interrupting the running of the period of prescription?