diff --git a/4-Templates/1b-TP.ipynb b/4-Templates/1b-TP.ipynb
index 76d18bd4e0ec1285be9c06ae0b8c51630e68aa3e..8d713ae8f5e8cdc8bd14c0a6a3c25d7e6fa1efee 100644
--- a/4-Templates/1b-TP.ipynb
+++ b/4-Templates/1b-TP.ipynb
@@ -14,7 +14,7 @@
    },
    "source": [
     "<h1>Table of contents<span class=\"tocSkip\"></span></h1>\n",
-    "<div class=\"toc\"><ul class=\"toc-item\"><li><span><a href=\"#Introduction\" data-toc-modified-id=\"Introduction-1\">Introduction</a></span></li><li><span><a href=\"#EXERCICE-37:-make-PowerOfTwoApprox-a-template-class\" data-toc-modified-id=\"EXERCICE-37:-make-PowerOfTwoApprox-a-template-class-2\">EXERCICE 37: make <code>PowerOfTwoApprox</code> a template class</a></span></li><li><span><a href=\"#EXERCICE-38:-consistency\" data-toc-modified-id=\"EXERCICE-38:-consistency-3\">EXERCICE 38: consistency</a></span></li><li><span><a href=\"#[optional]-EXERCICE-39:-crude-error-handling-for-the-overflow-issue\" data-toc-modified-id=\"[optional]-EXERCICE-39:-crude-error-handling-for-the-overflow-issue-4\">[optional] EXERCICE 39: crude error handling for the overflow issue</a></span></li><li><span><a href=\"#EXERCICE-40:-more-template-functions\" data-toc-modified-id=\"EXERCICE-40:-more-template-functions-5\">EXERCICE 40: more template functions</a></span></li><li><span><a href=\"#EXERCICE-41:-another-error-handling...\" data-toc-modified-id=\"EXERCICE-41:-another-error-handling...-6\">EXERCICE 41: another error handling...</a></span></li></ul></div>"
+    "<div class=\"toc\"><ul class=\"toc-item\"><li><span><a href=\"#Introduction\" data-toc-modified-id=\"Introduction-1\">Introduction</a></span></li><li><span><a href=\"#EXERCICE-37:-make-PowerOfTwoApprox-a-template-class\" data-toc-modified-id=\"EXERCICE-37:-make-PowerOfTwoApprox-a-template-class-2\">EXERCICE 37: make <code>PowerOfTwoApprox</code> a template class</a></span></li><li><span><a href=\"#EXERCICE-38:-consistency\" data-toc-modified-id=\"EXERCICE-38:-consistency-3\">EXERCICE 38: consistency</a></span></li><li><span><a href=\"#[optional]-EXERCICE-39:-crude-error-handling-for-the-overflow-issue\" data-toc-modified-id=\"[optional]-EXERCICE-39:-crude-error-handling-for-the-overflow-issue-4\">[optional] EXERCICE 39: crude error handling for the overflow issue</a></span></li><li><span><a href=\"#EXERCICE-40:-more-template-functions\" data-toc-modified-id=\"EXERCICE-40:-more-template-functions-5\">EXERCICE 40: more template functions</a></span></li><li><span><a href=\"#[optional]-EXERCICE-41:-another-error-handling...\" data-toc-modified-id=\"[optional]-EXERCICE-41:-another-error-handling...-6\">[optional] EXERCICE 41: another error handling...</a></span></li></ul></div>"
    ]
   },
   {
@@ -217,7 +217,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### EXERCICE 41: another error handling...\n",
+    "### [optional] EXERCICE 41: another error handling...\n",
     "\n",
     "_Optional: you may want to take the solution directly!_\n",
     "\n",