Please help me with b and c.​

What is the result of multiplying (2.5 × 1010) × (2.0 × 10-7)? a. 5.0 × 103 b. 5.0 × 10-3 c. 5.0 × 1017 d. 5.0 × 10-17

Explain which group an element with the electron configuration 1s2 2s2 2p6 3s2 3p6 3d1 4s2 belongs to.

Choose all the answers that apply. as ocean depth increases, temperature decreases temperature increases pressure increases pressure decreases salinity increases density increases