Answer:
Step-by-step explanation: 3 or 4th option
20,809,204 is the answer because 20,000,000+800,000+9,000+200+4
To model half-life, use the formula

. Here,

is the amount remaining after a length of time

.

is the amount that you start with.

is the half-life. You plug in 50 for

, 10 for

, and 25 for

. You get

.
It would be negative seeing the key word is down. (:
Hope I could help!
Part of a line but has 2 end point, extends in no direction. example: @
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