A linear octasaccharide (molar mass $=1024 \mathrm{~g} \mathrm{~mol}^{-1}$ ) on complete hydrolysis produces three monosaccharides: ribose, 2-deoxyribose and glucose. The amount of 2-deoxyribose formed is $58.26 \%(\mathrm{w} / \mathrm{w})$ of the total amount of the monosaccharides produced in the hydrolyzed products. The number of ribose unit(s) present in one molecule of octasaccharide is $\_\_\_\_$ . CASACCA - Use: Molar mass (in $\mathrm{g} \mathrm{mol}^{-1}$ ) : ribose $=150,2$-deoxyribose $=134$, glucose $=180$; Atomic mass (in amu): $\mathrm{H}=1, \mathrm{O}=16$