What is AB? A= [3 6]
[8 7]
[2 2]

B= [7 9]
[8 -2]
[-5 2]

answer: i think it is (1,-2)

probably the last option

step-by-step explanation:

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: