-20
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If $\det \mathbf{A} = 4$ and $\det \mathbf{B} = -5,$ then find $\det (\mathbf{A} \mathbf{B}).$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
-20
If $\det \mathbf{A} = 4$ and $\det \mathbf{B} = -5,$ then find $\det (\mathbf{A} \mathbf{B}).$
train