Logic Puzzle : Snack Attack

Snack Attack (Elementary level, story by Steph) 

based on the books by the awesome J. K. Rowling

With end of year exams only a week away, the Gryffindor common room was unusually empty and unusually quiet, unless you counted the hiss of the sulphurous green smoke flooding out of Hermione's ears.  Harry smothered a chuckle--Hermione was embarrassed enough already.  He kept his eyes focused on the book in front of him and munched a handful of sweets, silently renewing his vow to never so much as lick any foodstuff offered to him by Fred or George and thinking that at least Hermione's smoking ears had served the purpose of clearing people from the room, thus making studying easier.  Ron was trying valiantly not to laugh, but Harry had seen the mischievous glint in his eye and knew he was plotting to enrich the coffers of Weasley's Wizard Wheezes by purchasing some smoking smarties and delivering them via anonymous owl to Draco Malfoy. 

"Here," Ron dropped his quill on the table and pushed a bowl of snacks toward Hermione.  "Maybe this will help. ..er. . .clear your head."

"No, thank you," said Hermione composedly, not looking up from the thick textbook she was studying.  "I'm all set."  She patted the open package of snacks next to her, a package she had purchased herself at Honeydukes.  Having spent the last half an hour engulfed in the odor of rotten eggs, Hermione wasn't taking any more chances. 

Ron slunk across the room and pushed open a window, bringing a flower-scented breeze wafting into the room.  He picked up his quill, groaned, and got back to studying, pausing occasionally to snack from his own stash of sweets (purchased by himself and kept on his person thereafter.  Following an unfortunate Nose Hair Caramel incident, Ron too had learned to be wary of unattended food). 

Can you tell from the following clues who (Harry, Ron, Hermione) was studying what subject (transfiguration, potions, charms) and which snack they were eating (Pumpkin pasties, chocolate frogs and Bertie Bott's Every Flavor Beans)?

1. The student who ate the chocolate frogs had already finished transfiguration (and so was working on something else).
2. The three students were Harry, the one who ate pumpkin pasties and the one studying transfiguration.
3.  Ron was not doing his charms homework but Harry was struggling with his Potions assignment.