Consider the question. Maci is planning for the new school year and goes to the store to buy pens. She needs ten blue pens and 15 red pens. If a blue pen costs ten cents each and a red pen costs twice as much as the blue pen, how much money does Maci pay for the pens?
 If the answer is '4'; explain the reasoning:
Maci pays 10 * $0.10 = $1 for the blue pens. Each red pen costs 2 * $0.10 = $0.20. She pays 15 * $0.20 = $3.00 for the red pens. To buy all the pens she needs, Maci pays $3 + $1 = $4.