(1) Papsie appointed Asie, as agent, who in turn, appointed Sarsie as subagent to perform that which Asie was supposed to do for Papsie.

(a) Is the substitution valid?

(b) Is Asie liable to Papsie for damages caused by Sarsie's negligence?

(c) Assuming that the substitution was authorized, may Asie be still liable for Sarsie's negligence?

(2) Popoy, principal, authorized Ayoy, agent, to sell the former's car for not less than P500,000.00. Ayoy sold the car for P550,000.00. Is Ayoy entitled to the P50,000.00 overprice?

(3) Popoy, principal, authorized Ayoy, agent, to sell the former's car for not less than P500,000.00. Can Ayoy buy the car for P500,000?