Suppose that Isabella has 90 hours per week to allocate between work and leisure and she earns $12 per hour. Further, if she has the utility function represented by U(Y.L) = YL (that is Y multiplied by L), where Y is the total income and L is the amount of leisure. What is Isabella's optimal choice of leisure (L') if her non-labour income is zero? OAL" = 45 hours OB. L = 50 hours OC L = 55 hours OD. L' = 40 hours