In a question a student was given to find the derivative of the product of two functions $fandg\dot{}$ The student by mistake thought ${\left(fg\right)}^{{}^{\prime }}=f^{\prime }{g}^{\prime }$ for his question $f\left(x\right)=x^3$ and he got the correct answer. Given that $g\left(4\right)=1.$ Then which of the following is false? $g\left(5\right)=\frac{1}{8}$ b. $f^{prime}\left(x\right)<0$ c.$f\left(0\right)<0$ d. none of these

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