This is shown in Figure 9-1, where the m and m schedules show the value of the marginal benefit derived from spending successive dollars on x and y . the opportunity cost of spending a dollar on x is the loss of benefits due to not spending it on y. total expenditures should therefore be distributed between x and y so that the benefit derived from spending the last dollar on x will equate that derived from spending the last dollar on y. thus oa is spent on x and ob on y such that ac =bd, and oa + ob equals total permissible outlays. by equating the benefits derived from the marginal dollars on x and y ,we maximize the sum of the total benefits derived from x