Answer:
230.3cm^2
Step-by-step explanation:
surface area: sum of all faces
base: 12 x 2.5 = 30cm^2
back: 84 cm ^2
cross section x 2 = 7 x 2.5 = 17.5
use Pythagoras theorem to find the width of slope: 7^2 + 2.5^2 = 49 + 6.25 = 55.25. square root of 55.25 = 7.4
so, area of slope : 7.4 x 12 = 88.8cm^2
sum of all areas: 114 + 106.3 = 230.3
