Chemistry.

Dear Forum Experts, Can some one help with this problem?
An experiment was undergone with 50cm3 mixture of NaOH, Na2CO3 and NaHCO3. And mehyl orange, phenophtalien used as indicators The concentration of NaHCO3 is 0.2m0ldm3. at the beginning. When 0.5moldm3 HCl 50cm3 added to that Rose colour goes to orange colour, when adding more HCl the solution became red. The total HCl amount added is 80cm3. WHAT IS THE CONCENTRATION OF NaOH at the beginning? How to find this?
Thanks Senaka