Consider the following system: \[\begin{array}{cccccccccccc} x_1 & & & & & & & & & = & 4 \\ & & x_2 & + & x_3 & & & + & 3x_4 & = & 6 \\ & & & & & & x_5 & - & 4x_4 & = & 2 \end{array}\] Jon Doe tells you that he has found a solution with \(x_3 = 2\) and \(x_4=1\). What must be the value of \(x_2\) in John's solution?