Radon-222 Has a Half-Life of 3

Radon-222 has a half-life of 3.8 days.An air sample from a basement in Colorado was analyzed 5.0 days after it was collected and found to have a radon activity level of 0.17 Bq/L.What was the original activity of this sample?

A) 0.22 Bq/L
B) 0.32 Bq/L
C) 0.42 Bq/L
D) 0.62 Bq/L
E) 0.52 Bq/L