Suppose Benny starts at $(10, 3)$ and is crawling along the curve $y = f(x)$ as $x → 5^{+}$. At the same time, Bertha begins at $(0, 7)$ and is also crawling along the curve $y = f(x)$ as $x → 5^{–}$. If Benny and Bertha are in contact by cell phone, how will they know if $\lim\limits _ { x \rightarrow 5 } f ( x )$ exists?