When Bell Aircraft acquired Airborne Airplanes, the executives of the two companies identified key employees they needed for the combined companies' success. One of them was Tom, the vice president of engineering. The executives offered Tom a one$-$time bonus of $$\mathrm{25},\mathrm{000}$ if he stayed with the company for $\mathrm{12}$ months following the acquisition. In this scenario, Tom's $$\mathrm{25},\mathrm{000}$ represents merit pay $.$ a commission stock options. a differential piece rate. a retention bonus.