see the picture with letters attached to better understand the problem
we know that
surface area=area A +area B+area C+area D+area E+area F
area A=area F
area B=area area D
area C=area E
so
surface area=[2*1]+[4*2]+[4*1]+[4*2]+[4*1]+[2*1]----> 28 units²
the answer is
28 units²
