Answer:
The citizen, however, does not have to pay because the police officer has a pre existing duty.
Step-by-step explanation:
"Preexisting duty rule is a common-law rule of contract. It says that the rule that performance of an act by which a party is already contractually bound to perform does not constitute valid consideration for a new promise. In other words, a party's offer of a performance already required under an existing contract is an insufficient consideration for modification of the contract."
Then, the citizen doesn't have to pay because the police officer has an existing contract, and it's considered an insufficient consideration for modification of that contract.
Reference: US Legal, Inc, 2019. “Preexisting Duty Rule Law and Legal Definition.” Preexisting Duty Rule Law and Legal Definition | USLegal, Inc., 2019