How can supplication increase provision when provision, like the lifespan, is predetermined, and the lifespan neither increases nor decreases, and what is the benefit of work if provision is predetermined?

Supplication is an act of worship, and the means of provision may cease. Allah Almighty may answer supplications, and it repels afflictions and brings forth blessings and provisions. As for your question, "What is the benefit of work if provision is predestined like one's lifespan?", Allah Almighty has decreed destinies with their causes, and taking hold of the means does not contradict destiny. As for the benefit of striving despite the predestination of hardship, the Messenger of Allah, peace and blessings be upon him, said when he was asked: "What is the work, O Messenger of Allah?" He replied: "Work, for everyone is facilitated for what they were created for."