The owners keep reacting to one week's sales — 80% truffles last week, panic production, 30% this week. What they actually need is the flow: given what a customer bought last, what do they buy next? Put your class survey's own percentages into the table below — every cell starts at 0.25, which is a guess and nothing more — then step the mix forward and watch where it settles.
Row = what they bought last. Column = what they buy next. Each row must total 1.00, because a customer buys something. Nothing is corrected for you.
The starting mix v⁰ — a row vector. This one must total 1.00 too.