Find an expression relating the exponential growth rate k and the quadrupling time upper t4.

Pretty easy, the wolf population if it grows by a constant percentage it can be represented as an exponential function because the population grows and they would grow more each year if it is by the same percentage then the growth would be exponential. 

compound interest also continues to grow at a fixed percentage rate per year and it too can be represented as an exponential growth function.

all exponential growth functions can be represented by the formula.