Let's see...
Two short sides of the rectangle = 2 x 3 units = 6
and FOUR triangle legs (they are all of equal length)....you can use pythag theorom or distance formula for points
using pyhtag x^2+x^2 = 4^2
2x^2 =4^2
x^2 = 2 x = sqrt 2
FOUR of them = 4 sqrt 2 = 5.66 units 5.66 + 6 =11.66 units
It appears YOU GOT IT!!!!
Now work on the area.....add the rectangle area + TWO triangle areas = ?