Francis has an income of $60 and a utility function U(x1, x2) = 20x1/21 + x2. The price of good 1(nuts) is $5 and the price of good 2 (berries) is $1. How many units of berries will Francis demand?

a) 80

b) 40

c) 4

d) There is not enough information to determine the answer.

e) 10