A toboggan and rider, having a total mass of 150 kg, enter horizontally tangent to a 90° circular curve with a velocity VA and the angle  of "descent," measured from the horizontal

A toboggan and rider, having a total mass of 150 kg, enter horizontally tangent to a 90° circular curve with a velocity V_A and the angle  of "descent," measured from the horizontal in a vertical x — z plane, at which the toboggan exits at B. Neglect friction in the calculation. The radius r_B equals 57 m.