Answer: 
Step-by-step explanation:
Given
Julien's parents want $64,000 at the end of 3 years
The rate of interest is 10% annually
Suppose they invested P amount initially
So, compound interest, compounded monthly is
72 1/9
0.1 recurring of the number 1 is 1/9 of the number
Let's assume
It started in 2000
so, t=0 in 2000

we can use formula

we can plug value

In 2005, the same survey was made and the total amount of gamma ray bursts was 7.3 million
so, at t=2005-2000=5
P(t)=7.3 million
we can plug value and then we can solve for r


now, we can plug back

now, we have
P(t)=1 billion =1000 million
so, we can set it and then we can solve for t


approximately

Year is 2000+192
year is 2192................Answer
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