Rounded box around heading

Question

I was wondering if anyone would be willing to provide a code to replicate the attached image in TeX. It is simply a blue text box with rounded edges and a dotted (rather than dashed) line between the heading (I don't mind which font this is in) and a paragraph of extra information. The width of the box should be the same as the width of each line of text and currently I'm working in a document set on A4 Paper with left and right margins both at -0.5 cm, the top and bottom margins being 2 cm.

Answer 1

\documentclass{book}
\usepackage{xcolor}
\usepackage{tcolorbox}


\begin{document}

\begin{tcolorbox}[colback=white, colframe=blue]
bla
\tcblower
blub
\end{tcolorbox}

\end{document}