A firm has two variable factors and a production function y=f(x1,x2)=(x1+4x2)1/2. The price of output good is $4 and the price of factor 1 is $1. Suppose that the price of factor 2 increases from $3 to $6. What happens to the profit maximizing output?
a)output decreases by 15/9
b)output decreases by 10/3
c)output decreases by 2/3
d)output increases by 2/9
e)output increases by 2