How do you find the mass number in an atom?

Anton created a chart listing different types of materials.which best complete the chart? (a)x: copper y: glass(b)x: rubber y: copper(c)x: paper y: silicon(d)x: silicon y: glass

How much force must a locomotive exert on a 12840-kg boxcar to make it accelerate forward at 0.490 m/s2?

Ineed the answer to question 1 , i’m desperate