You might be overlooking into what I wrote. One truck can deliver about 8 m3 of concrete. If you need 100 m3, that's about 12 deliveries. This can be done if

You might be overlooking into what I wrote. One truck can deliver about 8 m3 of concrete. If you need 100 m3, that's about 12 deliveries. This can be done if 4 trucks make 3 deliveries each, or if 3 trucks make 4 deliveries each. The supplier has several trucks and while each one needs maintenance rarely, the fleet of them needs maintenance almost daily, so the supplier is likely to either over-provision (have a spare truck), or be able to procure one from his competitor across the street. "One of the trucks having an accident" is already planned in on the supplier level.