3. X-ray is a common radiation used in spectrometric methods, please try to answer the following questions: (a.) Please compare the design and operation of the x-ray tube with HCL. (b.) For the x-ray tube, calculate the minimum tube voltage required to excite the following lines. The numbers in parentheses are the wavelengths in A (ngstrm) for the corresponding absorption edges. (b-1.) K lines for Ca(3.064) (b-2.) K lines for Mg (0.496)