Explanation : Canonical form=SOP or POS
No of min/MAX terms=23=8.
Therefore, Canonical form will have 28 have terms.
Zero term canonical forms=8C0=1.
One term canonical forms=8C1=8.
Two term canonical forms=8C2=28
Similarly total number of canonical expressions=
8C0+8C1+8C2+8C3+8C4+8C5+8C6+8C7+8C8=256