Answer:
hes paid 13,640
Step-by-step explanation:
Answer:

Step-by-step explanation:
Let's use a start by using common denominators.
and 
Now, replace the original equation with the common denominators. 
Solve! 
20 = 40e^-0.1446t
e^-0.1446t = 0.5
t = ln 0.5 / -0.1446
t = 4.8 days
Daily failure rate = probability that it will not work on any particular day.