26. (5 points)
Pinocchio's nose grows or shrinks depending on what he says. Every time he tells 1 lie, his nose grows by $5 \mathrm{~cm}$; every time he tells 1 truth, his nose shrinks by $1 \mathrm{~cm}$. Initially, Pinocchio's nose is $11 \mathrm{~cm}$ long. After he has said 10 sentences, his nose is $13 \mathrm{~cm}$ long. If these 10 sentences are either true or false, then among these 10 sentences, there are $\qquad$ true sentences.
$8$