What is the approximate bandwidth of a 13-WPM International Morse Code transmission?

Explication

Morse speed converts to a keying rate of WPM ÷ 1.2, so 13 WPM is about 10.8 baud. The regulatory necessary-bandwidth formula brackets rather than pins the figure — about 32 Hz for a non-fading circuit and 54 Hz for a fading one — while the estimate customary in amateur practice, bandwidth in hertz ≈ 4 × WPM, lands exactly on the listed 52 Hz.