Q4. (Finding The Sparsest Solutions using Subspace Method (25%)) Solving the problem in (6) is hard. However, when one has more data (i.e., y), the problem can be solved more easily, under reasonable conditions. Consider a system of linear equations where vi=Ax,,i=1,.... L. (7) in which we have A RM*Y M 7 (5%) (d) Using (12), design a procedure to recover X. (5%)