If AAA is a 4×44 \times 44×4 matrix and A2=0A^2 = 0A2=0, what can we conclude about rank(A)rank(A)rank(A)?
rank(A)=4rank(A) = 4rank(A)=4
rank(A)≤2rank(A) \leq 2rank(A)≤2
rank(A)=0rank(A) = 0rank(A)=0
rank(A)=3rank(A) = 3rank(A)=3