- if i take 0 mg/kg cysteine, i need 21 mg/kg of methionine (not realistic)

- if i take 21 mg/kg of cysteine, i need 10.1 mg/kg of methionine (that's a lot of cysteine)

- they define the population safe intake for cysteine as the difference, but i'm not sure i'm following that, or that it makes sense (21-10.1 = 10.9)

so, 

f(0) = 21

f(21) = 10.1

f(10.9) = ?

if we approximate with a polynomial, the constant term is 21 because f(0) = 21.

we only have two terms, so we can only get a very simple approximation:

f(x) = ax + 21

f(21) = 21a + 21 = 10.1 <----> a = (10.1 - 21)/21 = -0.51904761904

so, f(x) = 21 - x*10.9/21.

then, f(10.9) = 15.3423809524

10.9*70 = 763 mg cysteine

21(1 - (10.9/21)^2)*70 = 1073.96666667 mg methionine

i can work with these rdis, but i don't know if that's enough cysteine for taurine & gluathione or not, yet. so, is that good enough?