B=20-7-5=8
C=20-5-B=20-5-8=7
Spaces before 4 =20-C-4=20-7-4=9
Spaces after 4 = Spaces before 20-4-4 =20-4-9=7
The space after D=20-4-4 =20-4-7=9.
E=20-D-4 =20-9-7=4.