Two organic compounds (A) and (B) have same empirical formula `CH_(2)O`. Vapour density of (B) is twice the vapour density of (A). (A) reduces Fehling solution but does not react with `NaHCO_(3)`. Compound (B) neither reacts with `NaHCO_(3)` nor reduces Fehiling solution. What are (A) and (B)? Also report an isomer of (B) if it reacts with `NaHCO_(3)`