根据内容回答下列各题. Not long ago, there lived in Auckland a working family who dreamed about a house of their own. Anyone then could read in the newspapers about the building companies who offered to put people into a new house 51 only a $1,000 deposit. Of course, the remainder had to be paid off with interest over a period of twenty years or so. The worker and his wife hopefully went to one of these companies 52 this wonderful offer. And the man in the office said．“Yes, sure. You bring along $1,000 and we can 53 you with a new house.” So the worker and his wife had to work hard and in twelve months’ time they returned to the building man with $1,000. But the man in the office said, “Look, I’m sorry, 54 we’ll need $1,500 now. Costs have gone up since we saw you last, you know.” The couple thought it over and decided it would not take very long to save the extra $500 if they worked hard. In six moths they worked 55 overtime and saved the $500 in spite of the high rent they had to pay for their flat. Back to the building man they 56 with their $1,500. But to their surprise he 57 the deposit was now $3,000. Now somewhat wiser, the worker said, “And the next time, I dare say we’ll find the deposit rising once more. How have we 58 save the extra $1,500?” “Well”, said the man, “I think we can stabilize the situation for about twelve months. By the time you come with $3,000, we will have had the house 59 for you. The couple left, sad at heart as they saw their dream house 60 . By the time they had saved the extra $1.500, no doubt the deposit would have become still higher, maybe $5,000, then $10,000 and then…! 51.