Mortdecai collects a total of 8x2 = <<8*2=16>>16 dozens of eggs.
He sells a total of 3 + 5 = <<3+5=8>>8 dozens of eggs.
So, 16 - 8 = <<16-8=8>>8 dozens of eggs are left.
After using 4 dozens of eggs to make a pie, 8 - 4 = <<8-4=4>>4 dozens of eggs are left.
Since there are 12 in 1 dozen, then Mortdecai donates 4 x 12 = <<4*12=48>>48 pieces of eggs to the charity.
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