I'LL ADMIT IT.
I do not know how to use a calculator.
For the idiots who don't know what abrasion is, this is for you.

abrasion |əˈbrā zh ən|
noun
the process of scraping or wearing away : the metal is resistant to abrasion.
• an area damaged by scraping or wearing away : there were cuts and abrasions to the lips and jaw.

Wikipedia definition.
Source: http://en.wikipedia.org/wiki/Abrasion_(medical)
In dermatology, abrasion is a wound caused by superficial damage to the skin, no deeper than the epidermis. It is less severe than a laceration and bleeding, if present, is minimal. Mild abrasions, also known as grazes or scrapes, do not scar bleed, but deep abrasions may lead to the formation of scar tissue. A more traumatic abrasion that removes all layers of skin is called an avulsion. An abrasion is less serious than a burn in that a burn destroys the proteins that make up the epidermis and disrupts the function of the epidermal cells, while an abrasion simply removes the outer layers of the epidermis, which is up to 100 layers thick depending on the area of the body.