The line \(l_1\) passes through the points \(A(3,-1)\) and \(B(7,2)\).
the point \((2,a)\) lies on the line \(l_1\), find the value of \(a\).[3]
The line \(l_2\) passes through the point \(D(0,8)\).
Let \(S_1\) and \(S_2\) be the sets of all points lying on \(l_1\) and \(l_2\) respectively.
Given that \(S_1\cap S_2=\varnothing\), find the equation of the line \(l_2\).[2]