diff --git a/Labs/06.rkt b/Labs/06.rkt
index 81275b9..4270ee7 100644
--- a/Labs/06.rkt
+++ b/Labs/06.rkt
@@ -38,20 +38,41 @@
            [(node b l r) (type-case (Optionof Number) (unbox b)
                            [(some b) (set-box! (node-b t1-r) (unbox (node-b t2-r)))]
                            [(none) (set-box! (node-b t1-l) (unbox (node-b t2-l)))])]
-           [else (void)])
+           [else (unify-trees! t1-l t1-r)])
          (type-case BoxTree t2-l
            [(node b l r) (type-case (Optionof Number) (unbox b)
                            [(some b) (set-box! (node-b t2-r) (unbox (node-b t1-r)))]
                            [(none) (set-box! (node-b t2-l) (unbox (node-b t1-l)))])]
-           [else (void)])
-         (unify-trees! t1-l t1-r)
-         (unify-trees! t2-l t2-r)))]))
+           [else (unify-trees! t2-l t2-r)])))]))
+
+; should only call set box once per branch
+; should probably call unify trees after calling set box
+; 
 
 (define (unify-trees! t1 t2)
   (cond
     [(and (mt? t1) (mt? t2)) (void)]
     [(or (mt? t1) (mt? t2)) (error 'unify-trees! "shape mismatch")]
     [else
+     (begin
+       (type-case (Optionof Number) (unbox (node-b t1))
+         [(some v1)
+          (type-case (Optionof Number) (unbox (node-b t2))
+            [(some v2) (if (eq? v1 v2)
+                           (type-case BoxTree (node-l t1)
+                             [(node b l r) (begin
+                                             (set-box! (node-b (node-r t1)) (unbox (node-b (node-r t2))))
+                                             (set-box! (node-b (node-l t2)) (unbox (node-b (node-l t1)))))]
+                             [(mt) (begin
+                                             (set-box! (node-b (node-l t1)) (unbox (node-b (node-l t2))))
+                                             (set-box! (node-b (node-r t2)) (unbox (node-b (node-r t1)))))])
+                       (error 'unify-trees! "value mismatch"))]
+            [(none) (begin
+                      (set-box! (node-b (node-l t1)) (unbox (node-b (node-l t2))))
+                      (set-box! (node-b (node-r t2)) (unbox (node-b (node-r t1)))))])]
+         [(none) (begin
+                   (unify-trees! (node-l t1) (node-r t1))
+                   (unify-trees! (node-l t2) (node-r t2)))]))]))