diff --git a/lab03/interp.lhs b/lab03/interp.lhs
index 2704bd3..6b0d2d1 100644
--- a/lab03/interp.lhs
+++ b/lab03/interp.lhs
@@ -85,7 +85,10 @@ You must complete the other cases.
 > evaluate :: Exp -> Val
 > evaluate ETrue = VTrue
 > evaluate EFalse = VFalse
-> evaluate (Eif e1 e2 e3) = error "TBD"
+> evaluate (Eif e1 e2 e3) =
+>   case evaluate e1 of
+>     VTrue  -> evaluate e2
+>     VFalse -> evaluate e3
 
 
 And here we have a couple of programs to test.