1. **State the problem:** We are given a polygon ABCDEF with forces acting on its sides, and we need to find the resultant force when point P is an alternative point on side BA. 2. **Understanding the problem:** The problem involves vector addition of forces acting along the sides of the polygon. The resultant force depends on the vector sum of all forces. 3. **Key concept:** The polygonal force system is in equilibrium if the vector sum of all forces is zero. If P is a point on side BA, the resultant force can be expressed in terms of P. 4. **Resultant force calculation:** If the original force on side BA is $P$, then the resultant force when considering point P on BA is the sum of all forces. Since the polygon is closed and forces are along sides, the resultant force is proportional to the number of sides times $P$. 5. **Answer:** The resultant force is $3P$. This corresponds to option (3).