Let \( E_1, E_2, E_3 \) be three mutually exclusive events such that \( P(E_1) = \dfrac{3+3p}{6} ,\ P(E_2) = \dfrac{2-p}{8} \) and \( P(E_3) = \dfrac{1-p}{2} \). If the maximum and minimum values of \( p \) are \( p_1 \) and \( p_2 \), then \( (p_1 + p_2) \) is equal to:
