I. Introduction
In recent years, crowdsourcing, in which service providers provide various services by outsourcing them to an unspecified number of workers, has attracted wide attention [8]. Crowd-sourcing consists of a client, a worker, and a service provider. A worker selects and executes a task that can be executed by his or herself and submits the results to a crowdsourcing system after completing the task. If the provided results are matched with those requested by the client, the worker can receive a reward as compensation for the task. Widely known examples of services using crowdsourcing include Amazon Mechanical Turk, Uber Taxi, Uber Eats, and Lancers.