Answer
$c=\frac{3}{\sqrt[4] 5}$
Work Step by Step
$$f(c)=M$$
$$c^{4}=M$$
$$c^{4}=\frac{1}{3-0}\int_{0}^{3}x^{4}dx$$
$$c^{4}=\frac{1}{3}\int_{0}^{3}x^{4}dx$$
$$3c^{4}=\int_{0}^{3}x^{4}dx$$
$$3c^{4}=[\frac{x^{5}}{5}]_{0}^{3}$$
$$3c^{4}=\frac{3^{5}}{5}-\frac{0^{5}}{5}$$
$$3c^{4}=\frac{3^{5}}{5}$$
$$c^{4}=\frac{3^{4}}{5}$$
$$c=\frac{3}{\sqrt[4] 5}$$