Answer:
4000
Step-by-step explanation:
Out of their sample half of the people are in favor meaning that half of the total are also in favor and half of 8000 is 4000
I hope this helps and please don't hesitate to ask if there is anything still unclear!
Your function is: 
Domain: $(-\infty, +\infty)-\{ 0 \}$ or $R-\{ 0 \}$
Range: $[-\frac{3}{2}, -\frac{1}{2}]$
Midline: $y=-1$