P4O6 reacts with water according to equation

P4O6 + 6H2O 4H3PO3

4H3PO3 + 8NaOH Na2HPO3 + 8H20

Overall reaction :

P4O6 + 8NaOH 4Na2HPO3 + 2H2O

Moles of P4O6 = 1.1/220 = 0.5

Acid formed by one mole of P4o6 requires = 8 mol

Acid formed by 0.005 mol of NaOH is present in 100mL solution

0.04 of NaOH is present in solution = 1000/0.1 *0.04 = 400mL