5.3.2.29 Various problems in the space

condition: Through the vertex of a right angle \( C \), an isosceles right triangle \( A B C \), a plane \( \alpha \) is drawn so that \( \alpha \) is parallel to the hypotenuse and makes an angle of 30° degrees with the leg. Find the angle between the plane \( A B C \) and \( \alpha \).