Hello from MrBillDoesMath!
Answer:
72
Discussion:
Total Surface area = area of pyramid base + 4 ( area of triangular face)
In our case this becomes
4*4 + 4( (1/2) (4)(7) ) =
= 16 + (2)(4)(7)
= 16 + 56
= 72
which is the first choice.
Note: the area of a triangular face was computed using (1/2) b h, which in our case is
(1/2) (4) (7)
Thank you,
MrB
