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?
Julia buys 4 * 3 = 
<gadget id="calculator">4*3</gadget>
<output>12</output>
12 pens.
Dorothy buys 12/2 = 
<gadget id="calculator">12/2</gadget>
<output>6</output>
6 pens.
The total number of pens purchased is 4 + 12 + 6 = 
<gadget id="calculator">4+12+6</gadget>
<output>22</output>
22 pens.
The total cost of the pens is 22 * $1.50 = $
<gadget id="calculator">22*1.5</gadget>
<output>33</output>
33.

<result>33</result>