How much does it cost to send a letter from Michigan to Illinois?

How much is it to mail a standard size and shape letter (eg of 10-20 grams in the UK, or under an ounce in the US), using airmail if the distance makes this appropriate, from {CAT {pp-move-indef Michigan, the U.S. state located in the Great Lakes Region of the United States of America to Illinois, the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country?

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Show reasoning Reasoning

I followed this chain of reasoning:

By calculation (generator: ["now@trueknowledge.com"]) I know that:
The current time is June 18th 2013, 07:19:26

I know from locally stored knowledge that:
Michigan is in the United States ([fact: ["151873901@trueknowledge.com"]])

Illinois is in the United States ([fact: ["1146057@trueknowledge.com"]])

Fact 1: 42 US cents is the cost of sending a letter between the United States and the United States ([fact: ["162570094@trueknowledge.com"]])

Fact 1 is true for December 27th 2008, 00:00:00 onwards ([fact: ["162570098@trueknowledge.com"]])

By calculation (generator: ["cost_sending_letter_between_places@trueknowledge.com"]) I know that:
Fact 2: 42 US cents is the cost of sending a letter between Michigan and Illinois

Fact 2 is true for December 27th 2008, 00:00:00 onwards

By calculation (generator: ["timeperiodtopoint@trueknowledge.com"]) I know that:
Fact 2 is true at June 18th 2013, 07:19:26

I used the following facts to provide this answer:

Michigan is or has been in the United States

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Illinois is or has been in the United States

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42 US cents has been the cost of sending a letter between the United States and the United States since at least December 27th 2008, 00:00:00

agree disagree edit