Solve the following problems and explain your answers briefly:

1. Meng, Rye, and Marc promised to pay Princez solidarily P30,000 on or before October 30 without need of demand. On the said date, Meng paid the whole amount to Princez.

a. How much can Meng collect from Marc and Rye?

b. Suppose Rye turns out to be insolvent, how much can Meng collect from him?

2. If there are two or more debtors in one and the same obligation, is their liability joint or solidary? Explain.

3. Nata borrowed P10,000 from Cobie. It was agreed that Nata could pay P10,000 or deliver his piano on June 14. On June 12, Nata informed Cobie that she will deliver her piano. Can Nata still change her mind and deliver the P10,000 instead considering that she was given the right of choice? Explain.

4. Nata sold her TV to Cobie but was given the option to deliver a refrigerator instead. If the TV was lost through Nata's fault, is she liable to Cobie?