Let be the most the manager can pay the suppliers.
Then, we know from the information given in the question that the manager needs a 30% markup based on cost.
Therefore, the guiding equation will be:
because $10 is the most people will pay for a neck warmer.
Thus, the above equation will become:
Thus, the most a manager can pay the suppliers for neck warmers and still keep the selling price at $10 is $7.69