Arithmetic:

ADDITION:
[(Sa + Da),(Sc + Dc)]
SUBTRACT:
[(Sa - Da),(Sc - Dc)]
MULTIPLY:
[Sa + Da - Sa×Da, Sc×(1 - Da) + Dc×(1 - Sa) + Sc×Dc]
DIVIDE:
[Sa + Da - Sa×Da, Sc×(1 - Da) + Dc×(1 - Sa) + Sc/Dc]
REPLACE:
[Sa, Sc] (fade = 1)

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