Under the book's first reckoning: ṭūl = three alifs, tawassuṭ = two alifs, and qaṣr = one alif. It also reports another reckoning: five, three and one alif respectively.
An alif is the source's traditional measure. These are reported alternatives, not an invitation to switch reckoning inconsistently in the same exercise.
Opening interactive controls...
Two measures reported by the text
Madd Lengths and Permissible Combinations — Ṭūl, Tawassuṭ, Qaṣr and Consistency
Under the book's first reckoning: ṭūl = three alifs, tawassuṭ = two alifs, and qaṣr = one alif. It also reports another reckoning: five, three and one alif respectively.
An alif is the source's traditional measure. These are reported alternatives, not an invitation to switch reckoning inconsistently in the same exercise.