Answer: The concentration of 
 will be
 will be 
 after 416 seconds have passed.
 after 416 seconds have passed.
Step-by-step explanation:
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = 

t = age of sample = ?
a = let initial amount of the reactant = 

a - x = amount left after decay process = 



The concentration of 
 will be
 will be 
 after 416 seconds have passed.
 after 416 seconds have passed.