The plane \( 2x - y + z = 4 \) intersects the line segment joining the points \( A(a, -2, 4) \) and \( B(2, b, -3) \) at the point \( C \) in the ratio \( 2 : 1 \) and the distance of the point \( C \) from the origin is \( \sqrt{5} \). If \( ab < 0 \) and \( P \) is the point \( (a - b, 2b - a) \) then \( CP^2 \) is equal to:
