Calculating breadth of coverage for TCGA Whole Exome Sequencing data

Question

[steve]

I downloaded a set of .maf files from TCGA, which appear to come from whole exome sequencing datasets (labeled as "WXS").

I need to know the breadth of coverage, i.e. number of megabases, for each data set.

Where do you get this value from? Is there a definitive resource that lists the number of megabases covered in a standard whole exome sequencing experiment? Or do I need a value per-dataset from each TCGA project's information? I am hoping I don't need to download every .bam file and calculate it from there...