diff --git a/Week 5/9 Ordinary Differential Equations.ipynb b/Week 5/9 Ordinary Differential Equations.ipynb
index 9b681f3..2365c9e 100644
--- a/Week 5/9 Ordinary Differential Equations.ipynb	
+++ b/Week 5/9 Ordinary Differential Equations.ipynb	
@@ -39,7 +39,7 @@
    "cell_type": "raw",
    "metadata": {},
    "source": [
-    "team_members = \"\""
+    "team_members = \"Koen Vendrig, Kees van Kempen\""
    ]
   },
   {
@@ -73,7 +73,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "deletable": false,
     "nbgrader": {
@@ -90,10 +90,7 @@
    },
    "outputs": [],
    "source": [
-    "# Import packages here ...\n",
-    "\n",
-    "# YOUR CODE HERE\n",
-    "raise NotImplementedError()"
+    "import numpy as np"
    ]
   },
   {
@@ -122,7 +119,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "deletable": false,
     "nbgrader": {
@@ -140,8 +137,30 @@
    "outputs": [],
    "source": [
     "def integrator(x, y0, f, phi):\n",
-    "    # YOUR CODE HERE\n",
-    "    raise NotImplementedError()"
+    "    \"\"\"\n",
+    "    Numerically solves the initial value problem given by ordinary differential equation\n",
+    "    f(x, y) = y' with initial value y0 using the Euler method.\n",
+    "\n",
+    "    Args:\n",
+    "        x:   size n + 1 numerical array\n",
+    "        y0:  an initial value to the function f\n",
+    "        f:   a callable function with signature (x, y), with x and y the current state\n",
+    "             of the system\n",
+    "        phi: a callable function with signature (x, y, f, i), with x and y the current state\n",
+    "             of the system, i the step number, and f as above\n",
+    "\n",
+    "    Returns:\n",
+    "        An n + 1 numerical array representing an approximate solution to y' = f(x, y)\n",
+    "        given initial value y0 and steps from x\n",
+    "    \"\"\"\n",
+    "    \n",
+    "    y    = np.zeros(len(x))\n",
+    "    y[0] = y0\n",
+    "    \n",
+    "    for i in range(len(y)):\n",
+    "        y[i] = y[i - 1] + (x[i] - x[i - 1])*f(x[i - 1], y[i - 1])\n",
+    "    \n",
+    "    return y"
    ]
   },
   {
@@ -164,8 +183,28 @@
    "outputs": [],
    "source": [
     "def phi_euler(x, y, f, i):\n",
-    "    # YOUR CODE HERE\n",
-    "    raise NotImplementedError()"
+    "    \"\"\"\n",
+    "    Numerically solves the initial value problem given by ordinary differential equation\n",
+    "    f(x, y) = y' with initial value y0 using the Euler method.\n",
+    "\n",
+    "    Args:\n",
+    "        x: a size n + 1 numerical array\n",
+    "        y: a size n + 1 numerical array with y[0] the initial value corresponding to x[0]\n",
+    "        f: a callable function with signature (x, y), with x and y the current state\n",
+    "           of the system\n",
+    "        i: a callable function with signature (x, y, f, i), with x and y the current state\n",
+    "           of the system, i the step number, and f as above\n",
+    "\n",
+    "    Returns:\n",
+    "        An n + 1 numerical array representing an approximate solution to y' = f(x, y)\n",
+    "        given initial value y0 and steps from x\n",
+    "    \"\"\"\n",
+    "    \n",
+    "    for i in range(len(y)):\n",
+    "        y[i] = y[i - 1] + (x[i] - x[i - 1])*f(x[i - 1], y[i - 1])\n",
+    "    \n",
+    "    return y\n",
+    "    "
    ]
   },
   {
@@ -542,7 +581,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3 (ipykernel)",
+   "display_name": "Python 3",
    "language": "python",
    "name": "python3"
   },