I am doing some work with Random Variables and Probability Density Functions. I have entered the following commands:
 
\[ScriptCapitalD] = TransformedDistribution[Abs[a - b] + Abs[u - v], 
                             {a \[Distributed] UniformDistribution[],
                              b \[Distributed] UniformDistribution[],                                                                      
                              u \[Distributed] UniformDistribution[],
                              v \[Distributed] UniformDistribution[]}]
PDF[\[ScriptCapitalD], x]
Everything works as it should, albeit slowly. When I ask for the plot via
 
Plot[PDF[\[ScriptCapitalD], x], {x, -2, 4}, Filling -> Axis]
things get super slow.
Does anyone know what I am doing wrong?