In art class, Cheol-su and Young-hee brought clay, but Cheol-su's clay was heavier than Young-hee's. When Young-hee removed 7/5 grams (g) from her clay and stuck it to Cheol-su’s clay, Young-hee’s clay was 81/20 grams (g) lighter than Cheol-su’s clay. Find the difference in weight between the clay that Cheol-su and Young-hee brought at first.
81/20 7/5 [OP_ADD] 7/5 [OP_ADD]
var_a = 4.05
var_b = 1.4
var_c = var_a + var_b
var_d = 1.4
var_e = var_c + var_d
print('{:.2f}'.format(round(var_e+1e-10,2)))