Please help

all a12 A = Let a21 (22 be a 2 x 2 matrix and supposed the columns of A satisfy the condition all a21 Check the correct statement(s) below (check all that apply) is a solution to the system A.TO The matrix A is singular The RREF of A is the identity matrix The system A.T = b has a unique solution for every 2 x 1 vector b