\textbf{113.} The figure below shows a portion of the graph of $f(x) = a\cos(bx + c)$. If $b > 0$, $0 < c < \pi$, and $\dfrac{ac}{b} = 0$, what is the value?
\textit{[Figure: Graph of a cosine function with amplitude $\frac{1}{3}$, showing one full cycle. The graph reaches a minimum of $-\frac{1}{3}$ and passes through key points at $x = \frac{3}{4}$ and $x = \frac{5}{4}$]}
(1) $\dfrac{1}{16}$
(2) $1$
(3) $\dfrac{1}{4\pi}$
(4) $\pi$
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