Answer: 6.93 years
Step-by-step explanation:
Given
Rate of interest is 
Future value is given by 
For the investment to double itself, i.e. 

It takes around 6.93 years to double the investment.
the answer is A couse divide all 5
The number is increasing by 2 every time.
78 x 2 = 156
-4 + 156 = 152
The 78th term is 152