The domain of discourse is a group working on a project at a company. One of the members of the group is named Sam. Define the following predicates. P(x, y): x knows y's phone number. (A person may or may not know their own phone number.) D(x): x missed the deadline. N(x): x is a new employee. Give a logical expression for each of the following sentences.

a. There is at least one new employee who missed the deadline.
b. Sam knows the phone number of everyone who missed the deadline.
c. There is a new employee who knows everyone's phone number.
d. Exactly one new employee missed the deadline.