Going from left to right on the aggregate demand curve, real GDP .

rises as price level falls

rises as price level rises

falls as price level falls

falls as price level rises

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.

answer; the federal reserve system;

because the early people found out about it.