7.4. Find the minimum value of the expression $\frac{13 x^{2}+24 x y+13 y^{2}+16 x+14 y+68}{\left(9-x^{2}-8 x y-16 y^{2}\right)^{5 / 2}}$. Round the answer to hundredths if necessary.
Answer: 0.26 (exact value: $\frac{7}{27}$).

Note. In variants 7.1 and 7.3, the exact values 0.15625 and 0.4375, respectively, are also counted as correct.