Adam's password is of six characters combining letters (not case sensitive) and numbers. Bob is using a password cracker, a software using brute force by running through all possible combinations to find out the correct password. If Bob's computer can search through 1 billion different combinations in one second, how long will Bob run through all test and find out Adam's password?

A. > 1 day

B. 6-24 hours

C. 1-5 mins

D. 10-30 mins

E. 1-6 hours

F. 5-10 mins

G. < 1 minute

H. 30-60 minutes

Multiple choice, please show work.