Answer:
0.56 milligrams
Step-by-step explanation:
Put 6 where t is and do the arithmetic.
M(6) = 50·e^(-0.75·6) = 50·e^-4.5 ≈ 0.56 . . . . milligrams

notice, it goes 4,6 then 4, 6 again, and so on and so on
based on whatever exponent it may have
now, you're being asked, what 214 will give? 4 or 6?
The answer is 255cm<span>²</span>