What is the wavelength corresponding to the most intense light emitted by a giant star of surface temperature 4400 k?

This can be calculated by applying Wein displacement law which is stated as follows;

Maximum wavelength (m) * Temperature (K) = 2.90 * 10^-3 m. K

Therefore, substituting for the values given;

Wavelength = (2.90*10^-3) / T = (2.90*10^-3) / 4400 = 6.59*10^-7 m ≈ 659 nm