A linear system AX=B
A= [1 2 3]
[4 5 6]
[7 c 9]

B= [1]


1) For what value of c are there no or infinitely many solutions?
2) For what value of b are there infinitely many solutions and what are they?
I know that c is obviously 8 but I cant figure out how to compute AX=B to obtain values of c and b. I even know that if c=8, there are infinitely many solutions. Please help me as I have been doing this for the past 2 days.