diff --git a/04-cost/04-cost.tex b/04-cost/04-cost.tex
index 81d25e9..2e5462f 100644
--- a/04-cost/04-cost.tex
+++ b/04-cost/04-cost.tex
@@ -35,6 +35,14 @@
   {After every phone call}
   {ccb, baseline}
 
+\pmbaQuestion
+  {What is the most honest way to bill a customer?}
+  {\$100 per hour}
+  {\$100 per line of code}
+  {\$100 per feature}
+  {\$100 per pull request}
+  {salary}
+
 \pmbaQuestion
   {How to calculate Cost Performance Indicator (CPI)?}
   {\(\texttt{CPI} = \texttt{EV} / \texttt{AC}\)} % CPI
@@ -53,20 +61,36 @@
 
 \pmbaQuestion
   {You are a project manager, a programmer asks you to pay \$500 for a training course about Machine Learning. What do you answer?}
-  {Definitely, not!}
-  {I have to ask our CFO and the customer}
-  {Only if you work on weekends}
-  {How ML is related to our project?}
+  {``Definitely, not!''}
+  {``I have to ask our CFO and the customer''}
+  {``Only if you work on weekends''}
+  {``How ML is related to our project?!''}
   {school}
 
 \pmbaQuestion
   {You just interviewed two programmers and now have to explain to the CEO that you want to hire the one that is more expensive; what is the best argument to use?}
-  {She has longer experience}
   {She is more enthusiastic about our project}
+  {She has longer experience}
   {She has bigger StackOverflow reputation}
-  {Her projects have more GitHub stars}
+  {She worked for our competitor before}
   {value}
 
+\pmbaQuestion
+  {Would you allow your team members know the salaries of each other?}
+  {Definitely, No!}
+  {Only if they are all the same}
+  {Only if they are all higher than the market can pay}
+  {Definitely, Yes!}
+  {salary}
+
+\pmbaQuestion
+  {Who is making more money?}
+  {OCJP}
+  {PMP}
+  {PhD}
+  {CEO}
+  {salary}
+
 \plush{
 \pptBanner{Earned Value Method}\par
 \pptPic{.8}{evm.png}\par
@@ -84,13 +108,18 @@
 
 \plush{
   \pptBanner{Homework:}
-  ``Project Estimate -- ...''
-  --- PMBOK5
+  A ``project estimate'' refers to a systematic assessment of the anticipated time, resources, and costs required to complete a specific project. It is derived from a detailed understanding of the project's scope, tasks, and potential challenges, and serves as a foundational tool for budgeting, scheduling, and resource allocation. Accurate project estimates are crucial for setting realistic expectations and ensuring the project's successful completion within its defined constraints.
+  --- ChatGPT 4.0
 }
 
 \plush{
   \pptBanner{Read this:}
-  % How much do you cost?
+  \nospell{Steve McConnell}, \emph{Software Estimation: Demystifying the Black Art} (2006)\par
+  \href{https://www.yegor256.com/2015/06/02/how-to-estimate-software-cost.html}{How Much For This Software?} (2015)\par
+  \href{https://www.yegor256.com/2018/01/09/micro-budgeting.html}{Five Stages of Microbudgeting} (2018)\par
+  \href{https://www.yegor256.com/2014/10/29/how-much-do-you-cost.html}{How Much Do You Cost?} (2014)\par
+  \href{https://www.yegor256.com/2014/04/11/cost-of-loc.html}{How Much Do You Pay Per Line of Code?} (2014)\par
+  \href{https://www.yegor256.com/2014/10/21/incremental-billing.html}{Incremental Billing} (2014)\par
 }
 
 \end{document}
diff --git a/aspell.en.pws b/aspell.en.pws
index 0bc22b7..59fb09e 100644
--- a/aspell.en.pws
+++ b/aspell.en.pws
@@ -23,4 +23,7 @@ COCOMO
 Standups
 Tetris
 durations
-StackOverflow
\ No newline at end of file
+StackOverflow
+OCJP
+Microbudgeting
+ChatGPT
\ No newline at end of file