Answer:
c) Any percentage less than 50 percent
Explanation:
In order for this redemption to be treated as an exchange under the "substantially disproportionate" test, Sam must own the lesser between 50% of the stock shares and 80% of his original stock share.
If Sam owned 70%, 80% of that would be:
[tex]S = 0.7*0.8=0.56=56\%[/tex]
Since 56% > 50%, then Sam must own less than 50% of Club stock in order for the redemption to be substantially disproportionate