Why is the code not running?

Question

Python

a=[0, 1, 5, 10, 44, 60, 34, 31, 79, 110, 111] 
a.sort()
while a[-1]%10!=0:
    a=a.pop()
else:
     print (str (a[-1]))

Answer 1

And what does a become equal to after this command?
a=a.pop()
and will this code work after that?
while a[-1]%10!=0:

Answer 2

The error is on the fifth line.
Do we have to come up with the code ourselves or can you show it to us?