When she is about to leave a restaurant counter, Mrs. Albanese sees that she has one penny,

Question:

When she is about to leave a restaurant counter, Mrs. Albanese sees that she has one penny, one nickel, one dime, one quarter, and one half-dollar. In how many ways can she leave some (at least one) of her coins for a tip if
(a) There are no restrictions?
(b) She wants to have some change left?
(c) She wants to leave at least 10 cents?