Challenge#4: Puzzles-a-Plenti

[Neo]

You know how they have those random puzzles in RE that don't make much sense? Well we've got those too! Hooray!
(just play along)

Billy is standing behind Rebecca and at the same time Rebecca is standing behind Billy. How is this possible?

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?

The T-Virus is released in Raccoon City. The virus doubles in concentration every minute. After exactly 20 minutes the entire city will be covered in the virus. After how many
minutes will half of the city be covered by the virus?


Please post answers by 9pm CST Thursday.
I will post a tie-breaker if both tribes answer these questions correctly.