For the given functions, find \( (f \circ g)(x) \) and \( (g \circ f)(x) \) and the domain of each. \[ f(x)=\frac{4}{1-7 x}, g(x)=\frac{1}{x} \] \( (f \circ g)(x)=\mid \quad \) (Simplify your answer.) \( (g \circ f)(x)=\quad( \) Simplify your answer. \( ) \) What is the domain of \( f \circ g \) ? A. \( (-\infty,-7) \cup(-7,0) \cup(0, \infty) \) B. \( (-\infty, 0) \cup(0,7) \cup(7, \infty) \) C. \( (-\infty, 7) \cup(7, \infty) \) D. \( (-\infty, 0) \cup(0, \infty) \) What is the domain of \( \mathrm{g} \circ \mathrm{f} \) ? A. \( \left(-\infty, \frac{1}{7}\right) \cup\left(\frac{1}{7}, \infty\right) \) B. \( (-\infty, 0) \cup(0, \infty) \) C. \( (-\infty, 7) \cup(7, \infty) \) D. \( (-\infty, 0) \cup\left(0, \frac{1}{7}\right) \cup\left(\frac{1}{7}, \infty\right) \)