George works for a small start$-$up that develops educational apps. His company offers a bonus of up to $20\%$ of his salary which is contingent on his performance as well as the company's performance. This type of compensation plan is also known as

$$ a$)$ fixed pay.

b$)$ gainsharing.

c$)$ perquisite.

d$)$ incentive pay.

$$ e$)$ benefit pay.