To maximize her utility, Elsa should allocate all her available labor time to bananas (LB = 10) and water (LW = 0).
To maximize her utility, Elsa should allocate her labor time between bananas and water in a way that maximizes her utility function U = BW. Since her production function for bananas is B = 2LB and her production function for water is W = 2LW, she needs to find the values of LB and LW that will maximize her utility.
Given that Elsa has a total of 10 hours available and her utility function is U = BW, she needs to find the values of LB and LW that maximize U = B*W = (2LB)(2LW) = 4LB*LW.
We can solve this problem using calculus by taking the partial derivative of U with respect to LB and LW and setting them equal to zero. This will give us the values of LB and LW that maximize U.
Taking the partial derivative of U with respect to LB, we get dU/dLB = 4LW = 0. Solving for LW, we find that LW = 0.
Taking the partial derivative of U with respect to LW, we get dU/dLW = 4LB = 0. Solving for LB, we find that LB = 0.
Therefore, to maximize her utility, Elsa should allocate all her available labor time to bananas (LB = 10) and water (LW = 0).