Axis Chemicals uses a weighted-avg process cost system to deal with the cost of synthesizing a chemical. To synthesize this chemical, a catalyst is used when the chemical is 55% done. Beginning work-in-process inventory for a month was 2k units, 70% done. In this month, 8k units were started in process and 7.5k were done. There were no losses or spoilage. If the ending inventory was 40% done, total equivlent units for the catalyst for this month was:

1. 2.5k
2. 10k
3. 7.5k
4. 8.5k
5. All of these options are false.

Which is correct, and why?