\[\boxed{\text{421\ (421).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[\textbf{а)}\ b^{4} \cdot b^{0} = b^{4} \cdot 1 = b^{4}\]
\[\textbf{б)}\ c^{5}\ :c{^\circ} = c^{5}\ \ :1 = c^{5}\]
\[\textbf{в)}\ a^{4} \cdot a{^\circ} = a^{4} \cdot 1 = a^{4}\]
\[\textbf{г)}\ x^{3}\ :x^{0} = x^{3}\ :1 = x^{3}\]