Jackie is doing a marginal analysis to decide if she should spend any more money on a movie download. after figuring out her marginal cost and marginal benefit, she will

After Jackie figures out her marginal cost and marginal benefit, she will be able to figure out efficient quantity.  To achieve efficient quantity, marginal cost and marginal benefits should be equal. Meaning, what people are willing to give up should be equal to the value that would be given up.

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

explanation:

productive can also mean:

producing or giving rise torelating to or engaged in the production of goods, crops, or other commodities.

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