I need help please and thank you

Me find the measure to side c and the process to solve the problem you appreciate it : )

Consider a cube that has sides of length l. now consider putting the largest sphere you can inside this cube without any point on the sphere lying outside of the cube. the volume ratio -volume of the sphere/ volume of the cube is 1. 5.2 × 10−1 2. 3.8 × 10−1 3. 1.9 4. 2.5 × 10−1 5. 3.8

Can somebody 1. what is the formula for finding the vertical distance between two points on a coordinate plane?