Find the least squares solution of the system $A\mathbf{x} = \mathbf{b}$, in which

and $\mathbf{b} = [4, -1, 0, 1]^T$. c is the rounding (or nearest) integer of the sum of the elements in $\mathbf{x}$. What is the value of mod(|c|,5), where mod(.) is the modulo operator?