\textbf{155.} The probability function is defined as $P(X = x) = \dfrac{\dbinom{5}{x}}{A}$\,;\; $x = 0, 1, 2, 3, 4, 5$. By calculating the value of $A$, what is $P(X = 2 \text{ or } X = 3)$?
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(1) $\dfrac{3}{8}$ \hfill (2) $\dfrac{7}{16}$ \hfill (3) $\dfrac{9}{16}$ \hfill (4) $\dfrac{5}{8}$
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