Two thin, concentric, coplanar circular loops lie in the x y-plane centered at the origin, as shown. The inner loop has radius \(R\) and carries a current \(I\) in the counterclockwise direction when viewed from the \(+z\)-axis. The outer loop has radius \(2R\) and carries a current \(2I\) in the clockwise direction. Which of the following correctly identifies the net magnetic field vector at the center of the loops (\(z = 0\)) and the direction of the net magnetic field along the \(+z\)-axis at a distance \(z \gg R\)?