What is the activity of 99Tc in a pharmaceutical after 1.5 hours?

[conniechiwa]

Homework Statement

*I'm only stuck on part c

During the testing process for some pharmaceuticals, the drug is "tagged" with a radioactive material. This way researchers can determine if the pharmaceutical is going to other parts of the body than the intended target and what effect it has on the non-target areas. By adding this radioactive tag to the pharmaceutical, researchers can pinpoint all parts of the body and the concentration that accumulates in non-target areas.

One possible such tag is technetium-99, 99Tc, which has a half-life of 6.05 hours.
a) How many 99Tc nuclei are required to give an activity of 1.6 μCi?
Answer: 1860176361

b) What is the decay constant for this isotope?
Answer: 0.11457 hour-1

c) Suppose the drug containing the amount of 99Tc calculated in part (a), were injected into the patient 1.5 hours after it was prepared, what would its activity be at that time?

Homework Equations

N=N0e^-λt
R=λN0
λ=ln2/T1/2

The Attempt at a Solution

N=N0e^-λt
N=(1860176361)e^-(0.11457 hour-1)(1.5 hours)
N=1566456874

λ=ln2/T1/2
λ=ln2/(6.05 hours* 60min/hour * 60 sec/min)
λ=3.18249E-5 hour-1

R=λN0
R=(3.18249E-5 hour-1)(1566456874)
R=49852.39512 Ci

I'm not sure what I did wrong...

 

[conniechiwa]

Nevermind. I ended up figuring out my mistake.