exercise 1 update

Author: yurchisin

optimization201/Modeling_Session_1/completed_exercise_set1.ipynb

@@ -143,7 +143,7 @@
         "**Q10.** Write `gurobipy` code using indicator constraints to model the following. Both parts reference the decision variables in the Modeling Example 1 notebook.\n",
         ">a. The link between $x_{p,d}$ and $y_p$.\n",
         "\n",
-        ">b. If Cleveland and Baltimore are open, then Charleston must be closed. "
+        ">b. If Cleveland and Baltimore are open, then Charleston must be closed. Feel free to add *auxiliary variables* if you want. "
       ]
     },
     {

optimization201/Modeling_Session_1/exercise_set1.ipynb

@@ -60,10 +60,10 @@
         "\n",
         "**Q7.** Write the `contrapositive` of \"If Duke is late for a meeting, that's because he was out surfing.\"\n",
         "\n",
-        "**Q8.** In the **Using Big M Constraints** section of this session's notebook, we used the following inequality $x + M_2 \\times z \\ge C$.\n",
-        ">a. Simplify this inequality using replacing $𝑀_2$ with $C$.\n",
+        "**Q8.** In the **Using Big M Constraints** section of last session's notebook, we used the following inequality $x + M_2 \\times z \\ge C$.\n",
+        ">a. Simplify this inequality replacing $𝑀_2$ with $C$.\n",
         "\n",
-        ">b. The other clause of the `OR` statement this comes from was $x \\le M_1\\times(1-z)$. Write out what these two inequalities reduce to when $z = 1$ and $z = 0$."
+        ">b. The other clause of this `OR` statement was $x \\le M_1\\times(1-z)$. Write out what these two inequalities reduce to when $z = 1$ and $z = 0$."
       ]
     },
     {
@@ -75,10 +75,10 @@
         "## Formulation and Coding\n",
         "**Q9.** In the **Constrainting production facilities** section of the Modeling Example 1 notebook, when adding the $y$ decision variables for opening production facilities, assume there are fixed costs, given by the list `[180, 150, 120, 155, 175]` for activating each respective distribution center. Write `gurobipy` code that will add these costs to the original objective function.\n",
         "\n",
-        "**Q10.** Write `gurobipy` code using indicator constraints to rewrite the following. Both parts reference the decision variables in the Modeling Example 1 notebook.\n",
+        "**Q10.** Write `gurobipy` code using indicator constraints to model the following. Both parts reference the decision variables in the Modeling Example 1 notebook.\n",
         ">a. The link between $x_{p,d}$ and $y_p$.\n",
         "\n",
-        ">b. If Cleveland and Baltimore are open, then Charleston must be closed. **Hint:* you may still need *auxiliary* variable(s).\n",
+        ">b. If Cleveland and Baltimore are open, then Charleston must be closed. Feel free to add *auxiliary variables* if you want. \n",
         "\n",
         "**Homework (optional):** Formulate the **Regional restriction** constraint as a big M constraint (this one may be a bit difficult for non-experts).\n",
         "\n",