Suppose the government wants to encourage lone parents to take part-time jobs and thinks 15 hours a week is consistent with children being in a crèche for 3 . hours a day, Monday to Friday. Which of the following might achieve the government's aim: (a) an additional lump-sum payment to lone parents, (b) a lower income tax rate for lone parents, or (c) a payment conditional on their taking at least 15 hours of work a week?