With the advent of techniques such as scanning tunneling microscopy, it is now possible to “write” with individual atoms by manipulating and arranging atoms on an atomic surface. 

a. If an image is prepared by manipulating iron atoms and their total mass is 1.05 × 10^-20 g, what number of iron atoms were used?

b. If the image is prepared on a platinum surface that is exactly 20 platinum atoms high and 14 platinum atoms wide, what is the mass (grams) of the atomic surface?

c. If the atomic surface were changed to ruthenium atoms and the same surface mass as determined in part b is used, what number of ruthenium atoms is needed to construct the surface?