Challenge#4: Puzzles-a-Plenti

[Jason1]

Originally Posted by Neo

A man decides to buy a zombie. He pays $60 for it, and he is very content with the flesh-eating undead. After a year, the value of the zombie has increased to $70 and he decides to sell the zombie. But already a few days later he regrets his decision to sell the blood-thirsty zombie, and he buys it again. Unfortunately he has to pay $80 to get it back, so he loses $10. After another year of owning the zombie, he finally decides to sell the zombie for $90. How much total profit does the man make?

10$

I also know the answer to #1, but Id rather not ruin it. Too easy IMO. The third one im not so sure on though...

Oh yea, Im just a reject, I dont matter.