How to write an action plan

Hi All
I have to write an action plan after i sent a couple of shipments, over weight. Normally i count the units but i must have miss counted so completely my fault i think a new set of scales are in order. Also they said the boxes are non standard as the have to much tape on them again me using second hand boxes.
i have to include the following

We would kindly ask you to provide us a detailed plan of actions you are going to take in order to prevent the re-occurrence of the above mentioned issue.

Please make sure to include the following information in your plan of action:
1.Feedback on all issues mentioned above
2.Steps and measures for how to avoid similar problems in future shipments
3.Estimated time-frame for implementation

We look forward to hearing from you.

Any suggestions i thought
1 admit responsibility. Mention i have read the guidelines in the 2 links they sent me.
2 explain I’ve brought a bulk consignment of new boxes and will purchase scales, i will include the invoice for the boxes. mention i will personally check every box complies.
3 this will be implemented immediately with all shipments from todays date.
4 Apologise

Does this sound about right
Tia