Can someone please check my work in calculating this area?

Okay, I needed to find the area of this figure: http://i25.tinypic.com/symtyt.jpg

So I figured out that each side had a total area of 224 (8*28), so the two combined would be 448, if they were separate. Since they overlap, I needed to subtract the area of the triangle from this. Using heron's formula, I plugged in the numbers: 1/2(14+14+8) --> square root of 18(18-14)(18-14)(18-8) --> square root of 18*4*4*10 --> square root of 2880. The square root of 2880 is 53.665.

So, I did 448-53.665=394. Is this correct?