Consider the 90Sr source and its decay chain from problem #6. You want to build a shield for this source and know that it and its daughter produce some high energy beta particles and moderate energy gamma rays. a. Use the NIST Estar database to find the CSDA range [in cm) and radiation yield for the primary beta particles in this problem assuming a copper and a lead shield. b. Based on your results in part a, explain which material is better for shielding these beta particles.