Machine output in two operating modes

A machine's normal output is \(x\) items per hour. In eco mode it produces \(y\) fewer items per hour, and in boost mode it produces \(y\) more items per hour.

1. In eco mode, the machine takes \(6\) hours to make \(240\) items. Form an equation in \(x\) and \(y\), and show that it simplifies to \(x-y=40\).[2]
2. In boost mode, the machine takes \(4\) hours to make \(240\) items. Form another equation in \(x\) and \(y\), and simplify it.[2]
3. Solve the equations obtained in (i) and (ii) to find \(x\) and \(y\).[3]
4. Hence, find the time needed to make \(240\) items in normal mode.[2]