A barn is an atomic unit of area equal to 10-28 m? What is the surface area of the Earth expressed in units of barn? Assume the Earth is a sphere with a radius of km. (The surface area of a sphere is 4t1r)? a 5.12 x 1042 barn O b. 5.12 x 10-20 bar O c. 5.12 x 1036 barn od 5.12 x 1030 barn e 5.12 x 10-14 barn Clear my choice