Andy worked weekends for a month to complete a difficult project. he hoped that he would receive a raise if he successfully completed the project. what could explain andy's motivation for working so hard

Andy’s motivation for working so hard is most likely the extrinsic motivation of a raise in his salary (money).

Extrinsic motivation refers to the phenomenon when behavior and actions are motivated by external factors, such as rewards, fame or praise rather than intrinsic factors which lie within an individual (such as: improving one’s skills and work ethic or genuine interest in the task or project at hand).

In Andy’s case, where he is working so hard in hopes for a raise, he is externally motivated rather than internally motivated since he hopes to be monetarily rewarded (extrinsic factor) for his hard work.