Tony will purchase new ribbon for his crafting projects. He will pay $8 per roll if 4 or fewer rolls are purchased, $6 per roll if 5 to 10 rolls are purchased, and $4 per roll if more than 10 rolls are purchased. a. Write a piecewise-defined function describing the cost of the rolls of ribbon. b. What is the cost of purchasing 3 rolls of ribbon? What is the cost of purchasing 6 rolls of ribbon?