I am confused about why the responses given are incorrect. I must be missing something in the process.

SummerFun, Inc., produces a variety of recreation and leisure products. The production manager has developed an aggregate forecast: Use the following information to develop aggregate plans. Click here for the Excel Data File Develop an aggregate plan using each of the following guidelines and compute the total cost for each plan. Hint: You will need extra output in April and August to accommodate demand in the following months. a. Use regular production. Supplement using inventory, overtime, and subcontracting as needed. No backlogs allowed. (Round your Average values to 1 decimal place. Negative amounts should be indicated by a minus sign. Leave no cells blank - be certain to enter " 0 " wherever required.)