If P stands for perimeter:
Perimeter of 1 triangle = 4 cm + 4 cm + 2.8 cm = 10.8 cm
28 mm is converted to cm to make all units similar.
1cm = 10 mm so, 28mm * 1cm/10mm = 28cm/10 = 2.8cm
There are 2 triangles: 10.8cm x 2 = 21.6 cm
We add up the length of 5cm, there are 3 lengths. 5 cm x 3 = 15cm
Perimeter = 21.6cm + 15 cm = 36.6cm
Among the choices, only the 1st option is closest to the answer at 36cm.
The 2nd choice is irrelevant because its unit of measure is in mm.