Answer: Exponential function: 
Step-by-step explanation:
Exponential function:  , a = initial value , x= time,  b= growth factor , b= 1+r , where r=rate of growth.
 , a = initial value , x= time,  b= growth factor , b= 1+r , where r=rate of growth.
Given: Initial population = a= 12,000, 
rate of growth = r= 5% = 0.05
Then, b=  1+r= 1+ 0.05 = 1.05
Substitute value of a and b in (i), we get

Hence, The required exponential function:  , where x= time.
, where x= time.