Calculus is an important branch of mathematics used to, as the title says, calculate the rate of change and the sum of infinitesimal parts. Today we're going to look at differential and integral equations and the application thereof. Now, class! Come on, I know it's boring but please, pay some attention - this is all very useful information. Gah, no one listens to me! This is so annoying, but I remember I knew some basic magic. I have tried to remember spells I've seen on my evening reads but I struggle to remember the word... Abra silenc... Abra ababra? Come on brain... Oh, nevermind, the spell must have worked, I asses after noticing that the class is paying attention to my every word. Now when the differentials deal with sum, the integrals on the other hand... I continue talking until I realize my clothes have gone missing!?