For any non-zero base, \(a^{0}=1\) and \(L^{0}=1\) regardless of the actual value of \(L\). Substituting:
\[O=(1-4\times1)^{6}=(-3)^{6}=729\]
Since \(L^{0}=1\) for every non-zero value of \(L\), the expression inside the bracket never changes as \(L\) varies, so the rate of change of output with respect to labour is:
\[\frac{dO}{dL}=0\]
The output stays fixed at 729 no matter how much labour is used.
Hence, the correct answer is Option C: Remains constant irrespective of the amount of labor.