The range in size of most atomic radii is approximately

5 × 10−11 m to 2 × 10−10 m
2 to 5 nm
5 × 10−21 m to 2 × 10−20 m
2 to 5 cm

The atomic radii is approximately between 5 × 10−11 m to 2 × 10−10 m

the answer is 1260

you spend 7 hours in school for 1 school day with 5 school days in 1 school week with 36 school weeks in a school year.

7*5*36= 1260 it's all about multiplying