Since diameter is given so it implies it is a regular hexagon.
The base of a regular hexagon can be divided into 6 equivalent triangles.
We know the side of the hexagon is 1.5 and radius of the base of hexagon is 1.25
so the height of center of the base to the side = sqrt(1.25^2 - 0.75^2) = 1
Therefore, area of one triangle = 1/2 * base * height = 1/2 * 1.5 * 1 =3
Since regular hexagon base consists of 6 equivalent triangles therefore the area of the base of hexagon = 6 * area of one triangle
=> Area of base = 6*3 = 18 units
Also regular hexagon have 6 slant surfaces, and all of them are equivalent triangle
So area of one of the slanted surface = 1/2 * slant height * side = 1/2 * 4 * 1.5 = 3
So total slant surface area = 6*3 = 18
Therefore, total surface area = 18 + 18 =36