Assertion (A): Given, length \(a\) \(=\) \(14\) \(cm\) and breadth \(=\) \(10\) \(cm\) of a reactangle. If, its length is decreased by \(m\) \(=\) \(1\) \(cm\) and breadth is increased by \(n\) \(=\) \(5\) \(cm\), then their difference in area is calculated using \(-mb + an - mn\).
Reason (R): Area of the rectangle \(=\) \(\text{length} \times \text{breadth}\)