find resolution of image from array of bytes

Array of eight bytes , i want to convert this first four bytes into 32-bit fixed point

number containing the horizontal resolution of image in pixels per inch , and the second four

bytes into 32-bit fixed point number containing the vertical resolution of image in pixels

per inch,how can i do that??

   byte []a=new byte[8] {0,72,0,0,0,72,0,0}  // array of bytes

it must find resolution of image in pixel by using this four bytes {0,72,0,0},use c#

language.