Dorothy, Julia, and Robert go to the store to buy school supplies. Dorothy buys half as many pens as Julia. Julia buys three times as many pens as Robert. Robert buys 4 pens. If one pen costs $1.50, how much money did the three friends spend in total on pens? Think carefully first, then make a decision:
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Julia buys 4 * 3 = 12 pens. Dorothy buys 12 / 2 = 6 pens. The total number of pens purchased is 4 + 12 + 6 = 22 pens. The total cost of the pens is 22 * $1.50 = $33. So, the answer is 33.
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