diff --git a/Assignments/03.rkt b/Assignments/03.rkt
index 389e18c..2d45e89 100644
--- a/Assignments/03.rkt
+++ b/Assignments/03.rkt
@@ -390,10 +390,15 @@
      (let* ([arg-type (parse-type te)]
             [res-type (typecheck body (BindType name arg-type env))])
        (arrowT arg-type res-type))]
-    [(listE elements) (begin
-                        (define type-list (map (lambda (x) (typecheck x env)) elements))
-                        
-     (listT )]
+    [(listE elements) (local [(define type-list (map (lambda (x) (typecheck x env)) elements))
+                              (define filtered (filter (lambda (x) (equal? (first type-list) x)) type-list))]
+                        (if (equal? filtered type-list)
+                            (listT (first type-list))
+                            (type-case Type (first type-list)
+                              [(varT v t) (if (none? (unbox t))
+                                            (listT (second type-list))
+                                            (error 'typecheck "no type"))]
+                              [else (error 'typecheck "no type")])))]
     ))
 ;; ----------------------------------------