AX2012 By Co products

Following are the types of cost allocation for By / Co product : 1.None,2.Manual & 3.TCA
What is the impact of selecting each of the type???

None

: no cost allocation is provided for the Co/By-product.

Manual:

enter the cost allocation percentage manually.

TCA

: This methodology allows the cost allocation calculation to be dynamic based on the quantity reported as finished using dollarized weighting.