diff --git a/3/rucksack.py b/3/rucksack.py
index 52e27e1..2eb6a33 100644
--- a/3/rucksack.py
+++ b/3/rucksack.py
@@ -3,9 +3,9 @@ import string
 from aocd.models import Puzzle
 from aocd import submit
 
-def eval_priority(rucksack: str) -> int:
+def eval_item_priority(rucksack: str) -> int:
     '''
-        evaluates the priority of a duplicate item
+        evaluates the priority of a common item
     '''
 
     # create a map of priority values
@@ -15,13 +15,28 @@ def eval_priority(rucksack: str) -> int:
     size = len(rucksack)
     a,b = rucksack[:size//2], rucksack[size//2:]
 
-    # find the duplicate item
-    duplicate = ''.join(
+    # find the common item
+    common = ''.join(
         set(a).intersection(b)
     )
 
     # return the priority
-    return priorities[duplicate]
+    return priorities[common]
+
+def eval_badge_priority(rucksacks: list) -> int:
+    '''
+        evaluate the priority of duplicate items over groups of three rucksacks
+    '''
+
+    # create a map of priority values
+    priorities = dict(zip(string.ascii_letters, range(1,53)))
+
+    # find common item among three sets
+    common = ''.join(
+        set(rucksacks[0]) & set(rucksacks[1]) & set(rucksacks[2])
+    )
+
+    return priorities[common]
 
 def parse_input(data: list) -> list:
     '''
@@ -35,10 +50,14 @@ if __name__ == "__main__":
     puzzle = Puzzle(year=2022, day=3)
     supplies = parse_input(puzzle.input_data)
 
-    # part a: determine the priority of all duplicate items
-    answer = sum([eval_priority(rucksack) for rucksack in supplies])
-    print(f'sum of priorities of all duplicate items: {answer}')
-    submit(answer, part='a', day=3, year=2022)
+    # part a: determine the priority of dupplicate items in compartments
+    answer_a = sum([eval_item_priority(rucksack) for rucksack in supplies])
+    print(f'sum of priorities of all common items amongst compartments: {answer_a}')
+    submit(answer_a, part='a', day=3, year=2022)
 
-    # part b:
-    #submit(total, part='b', day=3, year=2022)
+    # part b: determine the priority of common items in groups of three
+    # split the supply list into groups of three
+    rucksacks = [ supplies[i:i+3] for i in range(0,len(supplies),3) ]
+    answer_b = sum([ eval_badge_priority(rucksack) for rucksack in rucksacks ])
+    print(f'sum of priorities of all common items amongst groups of three: {answer_b}')
+    submit(answer_b, part='b', day=3, year=2022)