Problem 10.2 (2 points). Let A E Rnxd and y E R". The Ridge regression adds a l2 penalty to the least square problem: minimize 1/ Axc - yl12 + All20/12 with respect to x E Rd, (2) for some penalization parameter > > 0. (a) Without solving (2), show that (2) admits a unique solution. You can use HW9 results but you must justify everything precisely. (b) Show that this solution is given by Ridge = (ATA + Alda) ATy. Justify your answer precisely, including why (A A + Alda)-1 exists