I have Q, a 5 x 4 matrix and I need to find the conditions on b_1,b_2,b_3,b_4,b_5 that ensure that the system Qx=b has a solution by choosing an appropriate (A|b) and using Gaussian Elimination

how would I go about doing this?

should my a and b be

Q and b_1,b_2,b_3,b_4,b_5 respectively?

many thanks