求助两个改错

有两道KAPLAN改错，不理解.请指教.

NO.1

With adjustments for inflation, the relative cost of welfare benefits has been dropping since 1973, resulting in the welfare program now costing about 3 billion real dollars less to implement than it did.

Correct: and as a result the welfare program now costs about 3 million real dollars less to implement than it did.

NO.2

Although the author himself declared them  unpublished, the first appearance in print if 40 poems by TS is significant event , since they provide fascinating evidence about the creative process that were engaged in by this great Modernist.  

Correct: since they provide fascinating evidence about the creative process in which this great Modernist engaged.  

1，A，relative cost resulting in....,logic meaning is absurd.

2, active voice priors to passive voice .

Thanks.