Each of the following functions gives the amount of a substance present at time t. In each case, give the amount present initially (at t = 0), state whether the function represents exponential growth or decay, and give the percent growth or decay rate. 

(a) A = 100(1.07)^t 

(b) A = 5.3(1.054)^t 

(c) A = 3500(0.93)^t 

(d) A = 12(0.88)^t