A $3491$ by $3491$ square has its length decreased by $60$ and its width increased by $60$.  By how much does its area change?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
A $3491$ by $3491$ square has its length decreased by $60$ and its width increased by $60$.  By how much does its area change?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
3600
A $3491$ by $3491$ square has its length decreased by $60$ and its width increased by $60$.  By how much does its area change?
train