Express the Function in Terms of X $f ( u ) = u ^ { 5 }$

Multiple Choice

Express the function in terms of x.
-If $f ( u ) = u ^ { 5 }$ and $u = x ^ { 3 } + 8$ , then express $5 u ^ { 4 } \cdot 3 x ^ { 2 }$ in terms of $x$ alone.

A) $x ^ { 2 } \left( 15 x ^ { 3 } + 8 \right) ^ { 4 }$
B) $15 \left( x ^ { 5 } + 8 \right) ^ { 4 }$
C) $15 x ^ { 2 } \left( x ^ { 3 } + 8 \right) ^ { 4 }$
D) $\left( 15 x ^ { 5 } + 8 \right) ^ { 4 }$