please help me with #7 a) through h)

thank you :)

Describe what each line of the following MATLAB/Octave code does. Be specific, including sizes of any matrices created. (a) A-[1 2 -3; 5 -1 4; 0 0 2] (b) b=[6; 0; -2] - (c) I-eye (3) (d) [A,I] (e) Merref ([A,1]) (f) B=M(1:3,4:6) (g) x=B*b (h) A*x-b