ABC = 043 Respectively. Please help asap! Thank you very much!

Question 3) a) Explain the Bragg's law and necessary conditions for constructive interference (5 pts); b) Determine the expected diffraction angle ('O') for the first-order reflection from the (113) set of planes for FCC platinum when monochromatic radiation of wavelength 0.1ABC nm is used. The atomic radius of platinum is 0.1387 nm. (15 pts) (Use last three digits of your student registration number in ABC to solve this problem.)