we know that
[the surface area of the box]=2*[area of the base]+[perimeter of the base]*h
area of the base=6*10----> 60 in²
perimeter of the base=2*[6+10]----> 32 in
h=8 in
[the surface area of the box]=2*[60]+[32]*8-------> 376 in²
the answer is
376 in²