David Ungar holds a Dunkin' Donuts franchise. The terms of his franchise agreement require him to use only those ingredients furnished by Dunkin'

Donuts. He is also required to buy its napkins, cups, and so on, with the Dunkin' Donuts trademark on them. Is this an illegal tying arrangement? What if Dunkin' Donuts maintains that it needs these requirements to maintain its quality levels on a nationwide basis? [Ungar v. Dunkin' Donuts of America, Inc., 429 U.S. 823]

Please explain to me clearly, If I'm correct

I believe it's legal because he's advertising the franchise products to his customers.

Thank You