Let \( P \) be the plane passing through the line \( \dfrac{x-1}{1}=\dfrac{y-2}{-3}=\dfrac{z+5}{7} \) and the point \( (2,4,-3) \). If the image of the point \( (-1,3,4) \) in the plane \( P \) is \( (\alpha,\beta,\gamma) \) then \( \alpha+\beta+\gamma \) is equal to:
