3
In the text "An Introduction to Measure and Integration by Rana" i'm having trouble gaining intuition behind the following Proposition in $(1)$
$(1)$
$$\text{Proposition}$$
$\, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \,\, ...