Answer:
0.00116875 mg = 1.16875 micrograms
50 % decay 42 days = 10 x 4.2days = 0.0935mg = 93.5mcg
50% 12.6 days = 3 x 4.2 days = 0.0116875 mg = 1.16875mcg.
We check
Day group 1 = 40gm
Day group 2 = 20gm
Day group 3 = 10gm
Day group 4 = 5gm
Day group 5 = 2.5 gm
Day group 6 = 1.25gm
Day group 7 = 0.75mg
Day group 8 = 0.375mg
Day group 9 = 0.187mg
Day group 10 =0.0935mcg
Day group 11 = 0.04675mcg
Day group 12 = 0.023375mcg
Day group 13 = 0.0116875mcg
Step-by-step explanation: