H
R
=
O
t
/
E
t
,
C
h
e
m
o
b
e
f
o
r
e
S
u
r
g
e
r
y
O
t
/
E
t
C
h
e
m
o
A
f
t
e
r
S
u
r
g
e
r
y
=
6
/
2.620
3
/
6.380
=
4.870
Description:
Math equation.