Question 1033877
Okay, can you picture the height going from the center of the bottom to the very top of the pyramid?  If you draw a line from that point, along the base, you can see a right triangle that is 115 m at its base and 140 m tall, right?
The slant height of the pyramid's face can be figured using the Pythagorean Theorem...
Slant Height, call it c,
c^2  = a^2 + b^2 = 115^2 + 140^2
so that
c = 181.2 m
Now that slant height is the height of each triangular face, whose base is 230 m.  The area of a triangle is 
A = (1/2)bh = (1/2)(230)(181.2) = 20838 m^2
but there are four such faces so that the total surface area is
4A, or
83352 m^2