Answer: its b
Step-by-step explanation:
bc i used a calculator and it said so
Step-by-step explanation:
Exponential function is given by general form 
Where a and b are constants.
say a=1 and b=2 then we can write function as :

or 
To graph this or any exponential function, we just need to find some points then join them by a curved line.
Like plug x=0, 1, 2,... into above function and find points:
plug x=1

Hence point is (1,2)
Find more points similarly then graph them to get the graph as shown below:
180 seconds is 3 minutes. If you divide 156 by 3, you will get 52. If you are looking for 2 minutes, you have to multiply 52 by 2. The answer is 104 revolutions in 2 minutes.