Need help to understand this assembly for fibonacci seq

I understand the assembly properly. I am just confused about variable ‘b’ and ‘c’. It looks like b is stored at 12(%ebp). I conclude this from cmp 12(%ebp), %eax. If you look at func_8048516, it is adding -0x4(%ebp) which is ‘i’ and 12(%ebp) which is b. It should translate into a=b+i in the source code but it’s a=c+i. Can anyone explain this?