Answer: by commission
Explanation: In simple words, commission refers to the form of variable pay under which the sales person gets the part of the profit from the sale made by him.
In the given case, Hector has been described as a good salesman and is very efficient in his work. He is also very eager to make money.
Hence a commission job is best for him as he would get more money as many sales as he make.
Hence the correct option is b.