surface area = 1, 550

The formula for the area of a triangle is \(A=\frac{1}{2}bh\). Here, \(b = 12\space mm\) and \(h=7\space mm\).

A_{triangle}=\frac{1}{2}\times12\times7 = 42\space mm^{2}

Since there are 2 triangular bases, \(A_{triangles}=2\times42 = 84\space mm^{2}\)

There are 3 rectangular faces.

For the face with sides \(12\space mm\) and \(19\space mm\): \(A_{1}=12\times19=228\space mm^{2}\)
For the face with sides \(11\space mm\) and \(19\space mm\): \(A_{2}=11\times19 = 209\space mm^{2}\)
For the face with sides \(9\space mm\) and \(19\space mm\): \(A_{3}=9\times19=171\space mm^{2}\)

The total area of the rectangular faces is \(A_{rectangles}=228 + 209+171=608\space mm^{2}\)

The total surface area \(A = A_{triangles}+A_{rectangles}\)

A=84 + 608=692\space mm^{2}

\(692\space mm^{2}\)