Which mathematical product marketing innovation first introduced the 'try before you buy' model that allowed teachers to test educational software with their students before purchasing a full classroom license?

In the world of mathematics education products, marketing has evolved significantly over the decades. Companies have employed various strategies to promote learning tools, textbooks, and educational software. This trivia question explores a famous marketing innovation that revolutionized how mathematical concepts are sold and distributed to educational institutions and consumers.

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Texas Instruments' 'Classroom Preview Program' for graphing calculators (1992)
Mathematica's 'Time-Limited Full Functionality' licenses (1988)
MATLAB's 'Educator Evaluation Suite' (1994)
The Geometer's Sketchpad 'School Trial System' (1995)