diff --git a/plan.py b/plan.py
index 0bfdadf..33f007d 100755
--- a/plan.py
+++ b/plan.py
@@ -1,16 +1,16 @@
 #!/usr/bin/env python3
 
 import math
-import fractions
 import collections
 
-from typing import Dict
+from fractions import Fraction
+from typing import Dict, Iterable
 
 import satisfactory
 
 
-def calculate_rates(recipes, remain):
-    required_items = collections.defaultdict(fractions.Fraction)
+def calculate_rates(recipes: Iterable[str], remain: Dict[str,Fraction]):
+    required_items = collections.defaultdict(Fraction)
 
     while remain:
         for dst_name, dst_rate in remain.pop().items():
@@ -23,7 +23,7 @@ def calculate_rates(recipes, remain):
             dst_recipe = recipes[dst_name]['recipes'][0]
             src_recipe = recipes[dst_name]['recipes'][0]
 
-            normal_rate = fractions.Fraction(
+            normal_rate = Fraction(
                 dst_recipe['output'][dst_name],
                 dst_recipe['crafting_time']
             )
@@ -31,7 +31,7 @@ def calculate_rates(recipes, remain):
             scale = dst_rate / normal_rate
 
             for src_name, src_count in src_recipe['input'].items():
-                src_rate = fractions.Fraction(
+                src_rate = Fraction(
                     src_count,
                     dst_recipe['crafting_time']
                 ) * scale
@@ -40,14 +40,14 @@ def calculate_rates(recipes, remain):
     return required_items
 
 
-def basic_rate(recipe: Dict) -> fractions.Fraction:
+def basic_rate(recipe: Dict) -> Fraction:
     """
     Calculate the rate at which the item is crafted with the default recipe.
     :param recipe:
     :return:
     """
     for output, count in recipe['output'].items():
-        return fractions.Fraction(
+        return Fraction(
             count, recipe['crafting_time']
         )
 
@@ -59,7 +59,7 @@ conveyor_rates = [0, 60, 120, 270, 480, 780, 900]
 def main():
     recipes = satisfactory.Cookbook('data/recipes')
 
-    required_items = collections.defaultdict(fractions.Fraction)
+    required_items = collections.defaultdict(Fraction)
 
     # Create a list of items we want to make
     #targets = [ 'supercomputer' ]
@@ -89,7 +89,7 @@ def main():
 
         descriptor = recipes[name]
 
-        normal_rate = fractions.Fraction(
+        normal_rate = Fraction(
             descriptor['recipes'][0]['output'][name],
             descriptor['recipes'][0]['crafting_time']
         )