fully simplify (4a-b)^4

fully simplify (4a-b)^4

$\begin{array}{|rcll|} \hline && \mathbf{ (4a-b)^4 }\\ &=& (4a)^4 - 4\cdot(4a)^3\cdot b^1 + 6\cdot (4a)^2\cdot b^2 - 4\cdot (4a)^1\cdot b^3 + b^4 \\ &=& 4^4a^4 - 4\cdot4^3a^3\cdot b + 6\cdot 4^2a^2\cdot b^2 - 4\cdot 4a \cdot b^3 + b^4 \\ &=& 256a^4 - 4^4a^3\cdot b + 6\cdot 16a^2\cdot b^2 - 16a \cdot b^3 + b^4 \\ &\mathbf{=}& \mathbf{256 a^4 -256 a^3 b+96 a^2 b^2-16 a b^3+b^4 } \\ \hline \end{array}$