Answer:
There will be 6.5266 micrograms of Polonium-210 in his body after 85 days.
Explanation:
A continuously compounded decay can be modeled by the following expression:

Where "P" is the amount of Polonium-210 left after "t" days, "P0" is the initial amount of Polonium-210 and "d" is the decay rate. Replacing the known values into the expression yields:

There will be 6.5266 micrograms of Polonium-210 in his body after 85 days.
*Note that 0.502% = 0.00502.