1. Three printing presses, R, S, and T, working together at their respective constant rates, can do a certain printing job in 4 hours. S and T, working together at their respective constant rates, can do the same job in 5 hours. How many hours would it take R, working alone at its constant rate, to do the same job? A. 8 B. 10 C. 12 D. 15 E. 20 2. This year Henry will save a certain amount of his income, and he will spend t he rest. Next year Henry will have no income, but for each dollar that he saves this year, he will have 1 + r dollars available to spend. In terms of r, what fraction of his income should Henry save this year so that next year the amount he was available to spend will be equal to half the amount that he spends this year? A. 1/(r+2) B. 1/(2r+2) C. 1/(3r+2) D. 1/(r+3) E. 1/(2r+3) 两题答案都是E 麻烦大家帮我解答 万分感谢！！！ --

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