With the notation of question 28, show that
$$\mathbb { P } \left( M \notin \mathcal { G } \ell _ { n } ( \mathbb { R } ) \right) \leqslant \sum _ { j = 1 } ^ { n - 1 } \mathbb { P } \left( C _ { j + 1 } \in \operatorname { Vect } \left( C _ { 1 } , \ldots , C _ { j } \right) \right) .$$