A) Understand how iodine is used to treat disorder.

Here's how to help the patients understand their treatment and safety:

a) Understand how iodine is used to treat disorder.

Iodine-131 is a radioactive isotope that is selectively absorbed by the thyroid gland. It is used to treat thyroid disorders like hyperthyroidism (overactive thyroid) or thyroid cancer. The radiation emitted by Iodine-131 destroys overactive or cancerous thyroid cells, reducing their function or size.

b) Know when the substance will be safe.

The substance is considered safe when its activity drops below the background radiation level of 50 counts per minute. We first need to determine the half-life of the substance from the provided data.

Step 1: Determine the half-life ($T_{1/2}$) from