The efficiency of a fuel cell is given by

If 60% of a first order reaction was completed in 60 minutes, 50% of the same reaction would be completed in approximately
(log 4 = 0.60, log 5 = 0.69)

In a first-order reaction A $$ \to $$ B, if k is rate constant and initial concentration of the reactant A is 0.5 M, then the half-life is

The reaction of hydrogen and iodine monochloride is given as :
H_2(g) + 2ICl_(g) $$ \to $$ 2HCl_(g) + I_2(g)
This reaction is of first order with respect to H_2(g) and ICl_(g),
following mechanisms were proposed.

Mechanism A :
     H_2(g) + 2ICl_(g) $$ \to $$ 2HCl_(g) + I_2(g)
Mechanism B :
     H_2(g) + ICl_(g) $$ \to $$ HCl_(g) + HI_(g) ; slow
     HI_(g) + ICl_(g) $$ \to $$ HCl_(g) + I_2(g) ; fast

Which of the above mechanism(s) can be consistent with the given information about the reaction?