Solving a problem in physics section 42 point 26 optics

26. In the screen with a circular hole of radius r = 1,5 mm is normally incident parallel beam of monochromatic light of wavelength λ = 0,5 mm. The observation point is on the axis of the hole at a distance b = 1,5 m from it. Determine: 1) the number of Fresnel zones fit into the hole; 2) dark or bright ring seen in the center of the diffraction pattern when placed at the point of the screen.