In the following reaction sequence identify P, Q, R and S

$$\text{P} = \text{BF}_3$$, $$\text{Q} = \text{BCl}_3$$, $$\text{R} = \text{B}_2\text{H}_6$$, $$\text{S} = \text{B(OH)}_3$$

$$\text{P} = \text{NH}_4\text{BO}_2$$, $$\text{Q} = \text{B}_2\text{Cl}_4$$, $$\text{R} = \text{B(OH)}_3$$, $$\text{S} = \text{B(OH)}_4^-$$

$$\text{P} = \text{NH}_4\text{BO}_2$$, $$\text{Q} = \text{B(OH)}_3$$, $$\text{R} = \text{NaBO}_2$$, $$\text{S} = \text{B(OH)}_3$$

$$\text{P} = \text{BF}_3$$, $$\text{Q} = \text{B}_2\text{Cl}_4$$, $$\text{R} = \text{B(OH)}_3$$, $$\text{S} = \text{B(OH)}_4^-$$