The reaction A $$ \to $$ B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B?

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