Find the surface area of the figure, Please hurry and give an accurate answer

Given:

The base of the triangle = 5 mm

The other side of the of the triangle = 9 mm

The 3rd side of the triangle = 9 mm

The height of the triangle = 7 mm

The height of the prism = 12 mm

To find the surface area of the the prism.

Formula:

The surface area of a triangular prism is

Where,

h be the height of the triangle

H be the side of the prism

b be the base of the triangle

are the sides of the triangle.

Now,

Putting, b=5, H= 12, h=7, we get,

or,

or, sq mm

Hence,

The surface area of the triangular prism is 311 sq mm.

the least common denominator is 40

i would have to say it is c.