What number should replace the X to the magic square?

Reaching the end of a job interview, the Human Resources Person asked a young Engineer fresh out of MIT, "And what starting salary were you looking for?"

The Engineer said, "In the neighborhood of $125,000 a year, depending on the benefits package."

The interviewer said, "Well, what would you say to a package of 5 weeks vacation, 14 paid holidays, full medical and dental, a company matching retirement fund for 50% of your salary, and a company car leased every 2 years -- say, a red Corvette?"

The Engineer sat up straight and said, "Wow! Are you kidding?"

And the interviewer replied, "Yeah, but you started it."