The activation energy for a simple chemical reaction A $$\rightleftharpoons$$ B is E_$$a$$ in forward direction.
The activation energy for reverse reaction

2A $$ \to $$ B + C

It would be a zero order reaction when

When a bio-chemical reaction is carried out in laboratory, outside the human body in absence of enzyme, then rate of reaction obtained is 10^$$-$$6 times, the activation energy of reaction in the presence of enzyme is

For the reaction;

2N₂O₅ $$ \to $$ 4NO₂ + O₂ rate and rate constant are 1.02 $$ \times $$ 10^$$-$$4 and 3.4 $$ \times $$ 10^$$-$$5 sec^$$-$$1 respectively, then concentration of N₂O₅ at that time will be