Ambrose Has the Utility Function U(x₁, X₂)=4x^1/2₁ + X₂

Ambrose has the utility function U(x₁, x₂) =4x^1/2₁ + x₂.If Ambrose were initially consuming 4 units of nuts (good 1) and 27 units of berries (good 2) , then what is the largest number of berries that he would be willing to give up in return for an additional 21 units of nuts?

A) 5
B) 12
C) 6
D) 32
E) 3