Answer:
Surface area is 278.8cm^2
Finding Perpendicular height
C^2 - b^2 = a^2
49 - 4 =a^2
Square root both side to get a
A=3 root 5 or 6.7 to 1 d.p or the square root of 45
A=0.5bh
=0.5 x 4 x 3 root 5
=6 root 5 or 13.4 to 1d.p
=13.4 cm^2 each triangle
Two triangle is 26.8cm^2
(6 root 5 or 13.4 to 1 d.p x 2 = 12 root 5 or 26.8 to 1 d.p)
Rectangle area is 12 x 7 =84cm^2 each
84 x a total of 3 rectangles = 252 cm^2
Total area = 252 cm^2 + 26.8 is 278.8cm^2
Volume
V = area of cross-section (the triangle) x length
= 13.4 x 12
=160.8cm^2