Can someone answer. there is one problem. there is a picture. you!

SA=4pir^2
78.54km^2=SA
78.54=4pir^2
divide both sides by 4
19.635=pir^2
aprox pi=3.14 so divide both sides by 3.14
6.25318=r^2
sqrt both sides
2.50063=r
round
radius=2.5km

this question is flawed in that it gives the wrong units

answer is the option with 2.5 in it
2nd one

Ibelieve the second one, but if not, the first one will do. hope this : )