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diff --git a/coding-exercises/2/14.rkt b/coding-exercises/2/14.rkt
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+++ b/coding-exercises/2/14.rkt
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+#lang racket
+(require "../../shared/intervals.rkt")
+
+(define (print-interval-percent i)
+  (newline)
+  (display "interval{")
+  (display (center i))
+  (display ",")
+  (display (percent i))
+  (display "}")
+  (newline))
+
+(define (lem1 i1 i2)
+  (div-interval (mul-interval i1 i2)
+                (add-interval i1 i2)))
+
+(define (lem2 i1 i2)
+  (let ((one (make-center-percent 1.0 0)))
+    (div-interval 
+      one
+      (add-interval 
+        (div-interval one i1)
+        (div-interval one i2)))))
+
+;; adding scales the heighest percent to the new center
+(define (print-add)
+  (let ((i1 (make-center-percent 100.0 2.0))
+        (i2 (make-center-percent 200.0 3.0)))
+    (newline)
+    (println "*** add")
+    (print-interval-percent i1)
+    (print-interval-percent i2)
+    (print-interval-percent (add-interval i1 i1))
+    (print-interval-percent (add-interval i1 i2))
+    (print-interval-percent (sub-interval i1 i1))
+    (print-interval-percent (sub-interval i1 i2))))
+
+;; multiplication and addition of positive intervals
+;; adds percentage from both intervals
+(define (print-mul)
+  (let ((i1 (make-interval 2.0 8.0))
+        (i2 (make-interval 2.0 8.0)))
+    (newline)
+    (println "*** mul")
+    (print-interval-percent i1)
+    (print-interval-percent i2)
+    (print-interval-percent (div-interval i1 i1))
+    (print-interval-percent (div-interval i1 i2))
+    (print-interval-percent (mul-interval i1 i1))
+    (print-interval-percent (mul-interval i1 i2))))
+  
+;; There are at least some problems as I understand:
+;; 1. Repeated intervals in an equation are dependent on each other
+;; 2. Multiplicative identity is undefined and should not be uncertain
+(define (print-lem)
+  (let ((i1 (make-center-percent 100.0 2.0))
+        (i2 (make-center-percent 200.0 3.0)))
+    (newline)
+    (println "*** lem")
+    (print-interval-percent i1)
+    (print-interval-percent i2)
+    (print-interval-percent (lem1 i1 i2))
+    (print-interval-percent (lem2 i1 i2))))
+(print-add)
+(print-mul)
+(print-lem)