Answer: discharged by performance
Step-by-step explanation:
When parties to a contract are discharged from their duties as per the contract, it means that they are no longer party to the agreement. When this is done by performance, it means that the discharge was done because both parties have fulfilled the demands of the contract.
Bob agreed to tutor Lola for two hours and Lola agreed to pay Bob $50 for that. Bob then tutored her for the two hours and was paid the amount. The parties have therefore fulfilled their obligations to each other and so the contract has been satisfied.