Both
alcohol and vinegar evaporate at a constant rate upon boiling and
vinegar evaporates at three-fifth the rate of alcohol. At 12:10 p.m.,
Sanjana started boiling a mixture of alcohol and vinegar containing 60%
alcohol in order to reduce the concentration of alcohol to 40%. However,
she had to take a pause to make an urgent phone call at 12:20 p.m. by
which time the concentration of alcohol had reduced to 50%. If she
resumed the proceedings at 12:28 p.m., at what time was the desired
concentration of alcohol achieved? P.S.-Post Ur Strategy as well.

1) a 12:38 p.m.
2) b 12:29 p.m.
3) c 12:31 p.m.
4) d 12:33 p.m.