In an hour, the baker bakes 5 x 4 = <<5*4=20>>20 loaves of bread.
From Monday to Friday, he bakes 5 x 20 = <<5*20=100>>100 loaves of bread per day.
From Monday to Friday, he bakes a total of 100 x 5 = <<100*5=500>>500 loaves of bread.
On Saturday and Sunday, he bakes 2 x 20 = <<2*20=40>>40 loaves of bread per day.
On Saturday and Sunday, he bakes a total of 40 x 2 = <<40*2=80>>80 loaves of bread.
In a week, he bakes 500 + 80 = <<500+80=580>>580 loaves of bread.
In 3 weeks, he bakes 580 x 3 = <<580*3=1740>>1740 loaves of bread.
#### 1740