Add solutions to 3perOG chapter exercises

docs/book/content/UNtutorial/getting_started.md

@@ -32,7 +32,7 @@ For the October 21-25, 2024 United Nations `OG-PHL` training in Manila, we will
   - Theory: ["Simple" 3-period-lived agent model](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html)
 * - Tue.
   - Morning
-  - Review 3-period-lived-agent exercises <br> Review OG-Core and OG-PHL modules <br> Quick Git and GitHub workflow review
+  - Review 3-period-lived-agent exercises (solutions in [this folder](https://github.com/EAPD-DRB/OG-PHL/blob/main/docs/book/content/UNtutorial/solutions/3perOG/)) <br> Review OG-Core and OG-PHL modules <br> Quick Git and GitHub workflow review
 * -
   - Afternoon
   - Running OG-PHL, inputs, outputs <br> Calibrating OG-PHL, current state, still to do

docs/book/content/UNtutorial/solutions/3perOG/README.md

@@ -0,0 +1,14 @@
+# Solutions to the exercises in the 3-period-lived OG model chapter in the UN Tutorial section
+This folder contains the python scripts that compute the solutions to [Exercise 1](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html#ExerUNtut_3perOGfeas), [Exercise 2](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html#ExerUNtut_3perOGSS), and [Exercise 3](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html#ExerUNtut_3perOGTPI) in the "[A 'Simple' 3-period-lived agent OG model](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html)". In addition to this `README.md` file, this folder contains the following three Python scripts.
+- [`execute.py`](https://github.com/EAPD-DRB/OG-PHL/blob/main/docs/book/content/UNtutorial/solutions/3perOG/execute.py). This script runs everything and delivers the solutions to the exercises. It calls the following two modules [`SS.py`](https://github.com/EAPD-DRB/OG-PHL/blob/main/docs/book/content/UNtutorial/solutions/3perOG/SS.py) and [`TPI.py`](https://github.com/EAPD-DRB/OG-PHL/blob/main/docs/book/content/UNtutorial/solutions/3perOG/TPI.py).
+- [`SS.py`](https://github.com/EAPD-DRB/OG-PHL/blob/main/docs/book/content/UNtutorial/solutions/3perOG/SS.py). Python module that has the functions for solving the feasibility questions of [Exercise 1](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html#ExerUNtut_3perOGfeas) and the steady-state equilibrium questions of [Exercise 2](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html#ExerUNtut_3perOGSS).
+- [`TPI.py`](https://github.com/EAPD-DRB/OG-PHL/blob/main/docs/book/content/UNtutorial/solutions/3perOG/TPI.py). Python module that has the functions for solving the transition path equilibrium questions of [Exercise 3](https://eapd-drb.github.io/OG-PHL/content/UNtutorial/3perOG.html#ExerUNtut_3perOGTPI).
+
+You can run these computations that solve for the solutions to the three exercises by doing the following steps.
+1. Open your terminal windown (Mac or Linux) or Anaconda prompt (Windows).
+2. Activate your `ogphl-dev` conda environment: `conda activate ogphl-dev`
+3. Navigate to your `OG-PHL` repository directory.
+4. Navigate to the `/docs/book/content/UNtutorial/solutions/3perOG/` subfolder of this repository.
+5. Run the `execute.py` script: `python execute.py`.
+
+Running the `execute.py` script will print all the answers to the exercises in the output of the terminal. It will also create an `images` folder in this directory that has some of the images from the steady state and transition path equilibrium solutions.