What is the ruling and extent of Madd (prolongation) when connecting the first and second verses in Surat Al-Baqarah and Surat Al-Imran?

The first verse of Surat Al-Baqarah is "Alif, Lam, Mim." The Lam and Mim should be prolonged with a long madd (madd mushba') whether one stops or connects. As for the first verse of Surat Aal Imran, which is also "Alif, Lam, Mim," the reciter prolongs the Lam and Mim with a long madd when stopping. However, when connecting, reciters may choose between prolongation (madd) or shortening (qasr) for the Mim, due to the change in the cause of the madd, which is the sukoon.