A box containing 10 apples of the same weight was weighed and found to be 3.1 kg (kg). After removing one apple from the box, it became 2.81 kilograms (kg). Find the weight in kilograms (kg) of the empty box.
3.1 3.1 2.81 [OP_SUB] 10 [OP_MUL] [OP_SUB]
var_a = 3.1
var_b = 3.1
var_c = 2.81
var_d = var_b - var_c
var_e = 10
var_f = var_d * var_e
var_g = var_a - var_f
print('{:.2f}'.format(round(var_g+1e-10,2)))