Help :D .

The circunference is represented by the equation is .

The graph of this function is presented in the attachment.

Step-by-step explanation:

The general equation of the circunferece is defined by the following formula:

(1)

We can determine the value of the coefficients by knowing three distinct points: , ,

The system of linear equations is:

(2)

(3)

(4)

The solution of this system is: , , .

The circunference is represented by the equation is .

The graph of this function is presented in the attachment.

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

source: