No problem, scroll down the page if you are a math geek and you can even see and verify the calculations the site is based on and how the variables affect the result! There's a really nice tutorial there.
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. “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche
"We can judge the heart of a man by his treatment of animals." - Immanuel Kant