Answer:

Step-by-step explanation:
Suppose the electrician spends t hours at the house working.
Amount charged for every house call by electrician = $50
The electrician earned a total of $400 for a 5 hour job.
Also, C denotes total cost of the electrician's services.
So, the equation for C in terms of t is given below.

Here, 
If the half-life is t, then every t days, the amount of the radioactive isotope will be cut in half.
(1/2)^(number of half-lives) = 3%
number of half-lives = ln(0.03) / ln(0.5)
This gives the number of half-lives as 5.06.
Then 300 days = (5.06)(length of 1 half-life)
length of 1 half-life = 300 / 5.06 = 59.29 days
Answer:
4515
Step-by-step explanation: