In a cruel irony, it was not the Union army that laid waste to the city.
Source: Lincoln's Last Days: The Shocking Assassination that changed America Forever
In this sentence, irony means:
incongruity between what might be expected and
what occurs
O defiance of authority; disobedience
the quality of being consistent with or based on
logic
O a military offensive against an enemy

some attention getter quotes to support your thesis regarding brain work could be the following: :

a. storage capacity of your brain is virtually unlimited.

b. your brain produces sufficient electricity to light-up a small bulb.

c. different brain circuits are involved with reading aloud or silently.

d. your brain by itself does not feel pain.

e. reading allows your brain to download info directly.

f. brains of two musicians performing together can synchronize.

the economic activity signified in that scenario is a. production

in general, market production makes reference to the elaboration of a product or service which is destinated for economic purposes (to be sold) at money-price in a market. such product or service has to be principally tradable for money.

there is no money exchange involved in distribution, generalized reciprocity or balanced reciprocity.