How to crack wpa2???

admin & all members
i am new for hashcat user i want to know how to crack
A to F + 0 to 9 ( 8 length password )
i don't want to be use word list. only brute force attack
how many hours want to the crack time???
how to crack give me the code (mask)

My GPU MSI HD 7970 lightning
My PC i7
Memery 16GB