The rate of change of
is proportional to
.
When
,
.
When
,
.
The function is
.

Apply integral on each side.
\

Apply exponent on each side.
\

.
When
,
.
Substitute
.


.
Substitute
in
.
.
When
,
.
Substitute
in
.






.
Substitute
in
.
.
Find the value of
when
.
Substitute
and
in
.


.
.
.
.
.