The number of e. coli bacteria cells in a pond of stagnant water can be represented by the function below, where a represents the number of e. coli bacteria cells per 100 ml of water and t represents the time, in years, that has elapsed.

a(t)=136(1.123)^4t

based on the model, by approximately what percent does the number of e. coli bacteria cells increase each year?

a.

60%

b.

59%

c.

41%

d.

40%