The first thing you need to do, is to find the half life which is ( = (ln2)/k). To find it, we have to use the rate constant k The first order reaction has to be like this :[tex]ln[A] = ln[A]o -kt
at time t= 62 min[/tex] Then :[tex][A] = 67% [A]o
or 0.67[A]o[/tex] Then substitute these value and kind the k value. After substitution you can easily find what you were asked to find.
