Answer is 19.8 years
Step-by-step explanation: We will use the continuously compounded growth formula to solve this problem.
[tex]Q = Ne^k^t[/tex]
where Q is the final electric consumption,
N is the initial electric consumption,
e is the exponential function,
k is the rate of increasing (annually), and
t is the time in years.
As we are aware that final electric consumption is 4 times the initial consumption, so,
Q = 4N and k = 0.07
[tex]4N = Ne^k^t[/tex]
[tex]ln 4 = 0.07t[/tex] (as lne = 1)
t = 19.8 years
