Configuration for depreciation Keys for multiple calculations

Dear Experts

How to configure Depreciation key for MACRS-5 years and 7 years.

Also Please help me in understanding the  role of phases in Depreciation keys.

Client is having different percentages for 5 Years

1 year- 20%                         Diminishing Balance Method

2 Year-32%                        Diminishing Balance Method

3 Year -19.2%                     Diminishing Balance Method

4. Year -11.520%               Straight Line Method

5 Year-11.520%                 Straight Line Method

6 Year-5.760%                   Straight Line Method

Another scenario is for Special Depreciation is 50% in the 1^st year and for  the remaining 50% of the
acquisition value,  the above percentages are to be applied.

Need help in assignment of calculation method configuration. Please help me the configuration steps for this scenario.

Thanks in advance

Devi