How many free variables does each augmented matrix have? a. ⎣
⎡
​
1
0
0
​
9
0
0
​
−9
0
0
​
⎦
⎤
​
b. [ 1
0
​
2
0
​
−10
0
​
7
0
​
] c. ⎣
⎡
​
1
0
0
0
​
0
1
0
0
​
0
0
0
0
​
8
0
0
0
​
−8
−10
0
0
​
⎦
⎤
​
d. ⎣
⎡
​
1
0
0
​
0
1
0
​
−4
7
0
​
⎦
⎤
​
Note: In order to get credit for this problem all answers