a sneaker outlet has made the following wholesale purchases of new running shoes: 12 pairs at $45, 18 pairs at $40, and 20 pairs at $50. An inventory taken last week indicates that 23 pairs are still in stock. Calculate the cost of this inventory by FIFO.

Statements reasons 1. ab ? cd; ad ? bc 1. given 2. ac ? ac 2. reflexive property 3. ? adc ? ? cba 3. ? 4. ? dac ? ? bca; ? acd ? ? cab 4. cpctc 5. ? dac and ? bca are alt. int. ? s; ? acd and ? cab are alt. int. ? s 5. definition of alternate interior angles 6. ab ? cd; ad ? bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?