Answer:
La ingeniera lleva el cuaderno a los edificios; lo usa por la mañana. Después, me da el cuaderno para ayudar al jefe.
Step-by-step explanation:
The direct object is the one that replaces the noun. It must be substituted, ALWAYS, agreeing in gender and number to the substituted noun.
In this case, as the masculine singular noun ("cuaderno" is the notebook) is replaced by "lo".
MissSpanish