Process 1 produces P, Q, and R. The masses of P, Q, and R are 100 kg, 20 kg, and 5 kg, respectively, and their monetary values are $1000, $100, and $20. This process emits 500 kg of CO₂. Process 2 produces P and S with masses of 100 kg and 5 kg and monetary values of $1000 and $0. This process emits 1000 kg CO₂. Process 3 produces 1 kg of S with CO₂ emission of 0.8 kg. Choose the process for producing P that has the lowest CO₂ emission by using 

1. Mass-based allocation 

2. Monetary allocation 

3. Displacement and mass-based allocation 

4. Displacement and monetary allocation