On the ellipse \( \frac{x^2}{8} + \frac{y^2}{4} = 1 \) let \( P \) be a point in the second quadrant such that the tangent at \( P \) to the ellipse is perpendicular to the line \( x + 2y = 0 \). Let \( S \) and \( S' \) be the foci of the ellipse and \( e \) be its eccentricity. If \( A \) is the area of the triangle \( SPS' \) then, the value of \( (5 - e^2)A \) is:
