Dean Jones says:

"Sorry, but I've gone as low as I am prepared to go:  I'm going to insist on you supervising SIX Independent Study projects PER ACADEMIC YEAR.  Given the salary we are paying, this is my firm position."

Your response:

1.  "I've gone as high as I can go.  I must insist on FIVE per academic year...UNLESS you can raise my salary, say, to the 35th percentile.  Then I will accept SIX Independent Study projects.  After all, I am agreeing to teach five days a week."

2. "Very well...If You will raise my salary to the 35th percentile, then I'll accept the responsibility for SIX Independent study projects per year.  After all, I am agreeing to teach five days a week."