Given,

Frequency (f) = 1.44 x 10¹⁷Hz

Wavelength (λ) = speed (c) / frequency (f)

Speed (c) = wavelength (λ) x frequency (f)

= 2.09 x 10⁻⁹m x 1.44 x 10¹⁷Hz

= 3.0096 x 10⁸ m/sec ≈ 3.01 x 10⁸ m/sec

∴ speed (c) = 3.01 x 10⁸ m/sec.

in vacuum, it is always 299,792,458 m/s

1.44 ✕ 1017 Hz ?? that is meaningless

if not in vacuum, use λf = speed