The function given, \( a(t) = 5,000(1.12)^t \), represents exponential growth. In such a model, as time \( t \) increases, the amount \( a(t) \) grows slowly at first, but as \( t \) continues to increase, the growth rate accelerates, and the amount begins to increase more quickly.
Therefore, the correct answer is:
Option #1: As t increases, a increases slowly at first and then quickly.