With the notation of questions 23, 24 and 25, deduce that if $y \in \operatorname{Ext}(K)$ then the cardinality of $I_+(y) \cup I_-(y)$ is less than or equal to $k$.
With the notation of questions 23, 24 and 25, deduce that if $y \in \operatorname{Ext}(K)$ then the cardinality of $I_+(y) \cup I_-(y)$ is less than or equal to $k$.