Could use some help thanks

(a) You direct a 17.5 mW laser beam toward a surface at normal incidence. The surface is made of a material that completely absorbs the radiation. What is the radiation pressure on the surface if t diameter of 2.60 mm when it arrives at the surface? X How is the pressure related to the intensity of the incident beam? How is the intensity related to the power and cross-sectional area? N/m (b) You now direct the same laser beam, with the same power and beam cross section, at normal incidence on a mirror where 100% of the beam is reflected from the surface. What is the total pressure on it due to the incident and reflected energies? N/m2 Additional Materials Reading