What would the assignment fee be for a raw land deal?

[Trevor S Foster]

a family member has given me the opportunity to find a buyer for raw land that we own. It's 5.4 acres, appraisal is near 130k.  Land in the area similar have sold for between 110k and 140k. The homes built on similar land have sold for upwards of 400k. 

My 2 questions are:

1) If the appraisal for the land was determined to be 130k. After speaking with my family member, they've said they want 150k for the land maybe 140k. Am I wrong for thinking that we can't ask for more than what the appraisal has recommended?

2) What (in your opinion) would be a good assignment fee for a deal like this? 

Bonus question: what do you think the asking price should be for the land after looking at the appraisal and if a buyer were to accept, what (in your opinion) would you set the assignment fee at?