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Alison tried to find all the points on the curve given by $x^{2}+4 y^{2}=7+3 x y$ where the line tangent to the curve is horizontal. This is her solution:$\newline$Step $1$: Finding an expression for $\frac{d y}{d x}$.$\newline$$$\frac{d y}{d x}=\frac{3 y-2 x}{8 y-3 x}$$$\newline$Step $2$: Forming a system of equations.$\newline$$$\left\{\begin{array}{l} x^{2}+4 y^{2}=7+3 x y \\ 3 y-2 x=0 \\ 8 y-3 x \neq 0 \end{array}\right.$$$\newline$Step $3$: Solving the system.$\newline$$(3,2)$ and $(-3,-2)$$\newline$Is Alison's solution correct? If not, at which step did she make a mistake?$\newline$Choose $1$ answer:$\newline$(A) The solution is correct.$\newline$(B) Step $1$ is incorrect.$\newline$(C) Step $2$ is incorrect.$\newline$(D) Step $3$ is incorrect.