In a pack of construction paper, the numbers of blue and red sheets are originally in the ratio 2:7. Each day, Laura uses 1 blue sheet and 3 red sheets. One day, she uses 3 red sheets and the last blue sheet, leaving her with 15 red sheets. How many sheets of construction paper were in the pack originally?
(A) 144 (B) 252 (C) 135 (D) 270 (E) 105
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Source: CEMC, University of Waterloo,
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