By itself, the substitution effect of an increase in the wage rate will
a. always lead to an increase in the quantity of labor supplied
b. always lead to a decrease in the quantity of labor supplied
c. lead to an increase in the quantity of labor supplied only if leisure is like a normal good
d. lead to an increase in the quantity of labor supplied only if leisure is not a normal good
e. lead to an increase in the quantity of labor supplied only if the income effect works in the same direction