Answer
$D = 2.353 \times 10^{-3} J/Kg$
Work Step by Step
The dose in Gy resulted when energy divided by mass of the subject,
$D = \frac{0.2 J}{85 kg}$
$D = 2.353 \times 10^{-3} J/Kg$
*Note that 1 J/kg = 1 Gy
$D = 2.353 \space mGy$
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