Answer:
According to the passage, we have the next equation:

where "K" is a proportional constant
Leaving at the end with the next equation:

Integrating the equation, we have:

where "C" is a constant
Then, we have the 2 conditions for the problem:
1) t=0 → r=10
Replacing in the equation, we have C = 10
2) t=5 → r=8
Replacing in the equation, we have K = -0.4
Finally, the time which the snowball will be completely melted will be when r = 0. So replacing in the equation

t = 25 minutes
This would be true. The points make up a straight line
30,000+3,000+600+60+5 = 33665.
So you just add 10000 to 33665.
33665 + 10000 = 43665.