Can some one help me

How are natural numbers, whole numbers, integers, and rational numbers related

Linux is distributed under gnu gpl. why is this important? a. it ensures that only torvalds can profit from the sale of linux b. it prevents unknowledgeable users from downloading programs they don't know how to operate. c. it provides protection for the developers who created linux. d. it states that anyone can copy, modify, and share the program if changes are made public.

How do we use the sumif formula (when dealing with different formats) ?