When copper reacts with silver nitrate according to the equation, the number of grams of copper required to produce 432 grams of silver is -?

Answer is: mass of copper is 127 grams.
Balanced chemical reaction: Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s).
m(Ag) = 432 g. 
n(Ag) = m(Ag) ÷ M(Ag).
n(Ag) = 432 g ÷ 108 g/mol.
n(Ag) = 4 mol.
From chemical reaction: n(Ag) : n(Cu) = 2 : 1.
n(Cu) = 4 mol ÷ 2 = 2 mol.
m(Cu) = n(Cu) · M(Cu).
m(Cu) = 2 mol · 63.5 g/mol.
m(Cu) = 127 g.

Ithink the answer is 56.