请教一道英文的成本会计的题，附答案，求中文讲解，谢谢了

R company manufactures A product for use in its production line. the manufacturing cost per unit for 20000 units of A product is :
direct materials $6
direct manufacturing labor $30
variable manufacturing overhead $12
fixed manufacturing overhead allocated $16
total manu cost per unit $64
the T company has offered to sell 20000 units of A product to R company for $60 per unit. R company will make the decision to buy A from T company is an overall savings of at least $25000 for R company. if R company accepts T company's offer, $9 per unit of the fixed overhead allocated would be eliminated. Furthermore, R company has determined that the released facilities could be used to save relevant costs in the manufacture of B product. For R company to achieve an overall savings of $25000, the amount of relevant costs that would have to be saved by using the released facilities in the manufacture of B product would be?
答案：Costs of purchases, 20,000 units *$60 $1,200,000
Total relevant costs of making:
Variable manufacturing costs, $64 – $16 $48
Fixed costs eliminated 9
Costs saved by not making $57
Multiply by 20,000 units, so total
costs saved are $57 *20,000 1,140,000
Extra costs of purchasing outside 60,000
Minimum overall savings for Reno 25,000
Necessary relevant costs that would have
to be saved in manufacturing Part No. 575 $ 85,000

不理解那个$60000是什么意思啊，这道题的问题到底是什么意思我都搞不太懂，是用生产A 产品释放的材料来B产品可以省下多少相关费用吗？既然是这样的话直接自己生产花费1280000，买T公司的话花费1200000，那么省下的就是80000啊。。。
为什么要搞的这样乱七八糟呢