二、shortanswer(簡答題)(10%)

Suppose an individual derives his utility from spending $1000 income on two goods $x$ and $y$. His utility function is $U(x,y) = \sqrt{xy}$. The prices of two goods are $P_x = 10$ and $P_y = 20$.

(a) How many units of \( x \) and \( y \) does this individual consume to maximize his utility? (3%)