Rule 1: 1. The passive يُبَاعُ 'is sold'
بَاعَ / يَبِيعُ means to sell. Its passive imperfect is يُبَاعُ it is sold, with ḍamma on the prefix and a long ā in the middle. The thing sold is the subject, in the nominative, and the verb agrees with it: masculine يُبَاعُ, feminine تُبَاعُ; a plural of things takes the feminine singular. Nobody is named as the seller. In the same way يُقَالُ means it is said.
هُنَا يُبَاعُ الْخُبْزُ.
hunā yubāʿu-l-khubzu
Bread is sold here.
فِي هٰذَا الدُّكَّانِ تُبَاعُ الْفَاكِهَةُ.
fī hādha-d-dukkāni tubāʿu-l-fākihatu
Fruit is sold in this shop.
Feminine subject, feminine verb.
اَلْكُتُبُ تُبَاعُ فِي السُّوقِ الْقَدِيمَةِ.
al-kutubu tubāʿu fi-s-sūqi-l-qadīmati
Books are sold in the old market.
Non-human plural: feminine singular verb.
لَا يُبَاعُ الْقُمَاشُ هُنَا بَلْ فِي السُّوقِ.
lā yubāʿu-l-qumāshu hunā bal fi-s-sūqi
Cloth is not sold here but in the market.
يُقَالُ إِنَّ هٰذَا التَّاجِرَ غَنِيٌّ.
yuqālu inna hādha-t-tājira ghaniyyun
It is said that this merchant is rich.
After يُقَالُ, 'that' is إِنَّ with kasra, as after قَالَ (lesson 39).