20. Agents sometimes have liability to third parties for their actions taken for an on behalf of the principal. An agent will not be personally liable in which of the following circumstances?
a. If he makes a contract which he had no authority to make but which the principal raffles
b. If he commits a tort while engaged in the principal’s business
c. If he acts for a principal which he knows is nonexistent and the third party is unaware of this
d. If he acts for an undisclosed principal as long as the principal is subsequently