Let \(\overset{⃗}{a} = 2\hat{i}+\hat{k},\overset{⃗}{b} = \hat{i}+\hat{j}+\hat{k}\), and \(\overset{⃗}{c} = 4\hat{i}-3\hat{j}+7\hat{k}\). If \(\overset{⃗}{r}\) is a vector such that \(\overset{⃗}{r}\times \overset{⃗}{b} = \overset{⃗}{c}\times \overset{⃗}{b}\) and \(\overset{⃗}{r}\cdot \overset{⃗}{a} = 0\), Then \(\overset{⃗}{r}\cdot \overset{⃗}{c} =\)