The straight line \(l\) passes through the point \(P(-3, 6)\) and the point \(Q(1, -4)\).
- Find an equation for \(l\) in the form \(ax + by + c = 0\), where \(a\), \(b\) and \(c\) are integers. [4]
The straight line \(m\) has the equation \(2x + ky + 7 = 0\), where \(k\) is a constant.
Given that \(l\) and \(m\) are perpendicular,
- find the value of \(k\). [4]