Rank of a Matrix

How many solutions does the system of linear equations corresponding to the following augmented matrix have?
[101011011010000111000000]\left[ \begin{array}{rrrrr|r} 1&0&1&0&-1&1\\ 0&1&1&0&1&0\\ 0&0&0&1&1&-1\\ 0&0&0&0&0&0 \end{array} \right]
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