Two charges of \( 5Q \) and \( -2Q \) are situated at the points \( (3a, 0) \) and \( (-5a, 0) \) respectively. The electric flux through a sphere of radius \( 4a \) having center at origin is:
\( \frac{5Q}{\varepsilon_0} \)
\( \frac{7Q}{\varepsilon_0} \)
\( \frac{2Q}{\varepsilon_0} \)
\( \frac{3Q}{\varepsilon_0} \)