What I can do I will — Mathematics

What I can do-I will-1
Though it be little as a Daffodil-
That I cannot-must be
Unknown to possibility-
(F.641/J.361)
[1] What:: a math question.
[2] Daffodil:: a symbol of vanity.
[3] I cannot:: the math question that she cannot solve.
[4] possibility:: The condition of being a possible or real quantity in mathematics (OED 1e); a hint on the math. Unknown to possibility:: over the capability of her knowledge in math.