Let \( y = y(x) \) be the solution of the differential equation \( x^4 \, dy + \left(4x^3 y + 2 \sin x\right) \, dx = 0 \), \( x > 0 \), \( y\!\left(\frac{\pi}{2}\right) = 0 \). Then \( \pi^4 \, y\!\left(\frac{\pi}{3}\right) \) is equal to:
\( 64 \)
\( 81 \)
\( 92 \)
\( 72 \)
