Answer: 35.36
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Work Shown:
N(t) = N0*(1/2)^(t/5730)
N(t) = 200*(1/2)^(t/5730)
N(14325) = 200*(1/2)^(14325/5730)
N(14325) = 200*(1/2)^(2.5)
N(14325) = 200*0.17677669529663
N(14325) = 35.355339059326
N(14325) = 35.36
You were fairly close to the answer