Please choose the correct solution to the question: how to mix concrete for a slab

Solution1: A concrete mix of 1 part cement : 2 parts sand : 4 parts coarse aggregate should be used for a concrete slab. Ad water to proper consistency. Concrete must be placed after half an hour of mixing.

Solution2: A concrete mix of 1 part cement : 2 parts sand : 4 parts coarse aggregate should be used for a concrete slab. Ad water to proper consistency. Concrete must be placed within half an hour of mixing.

Answer format: solution1/solution2
Answer: solution2