We have already seen in the explanation for previous question, a sequence of routes which
takes 171 hours and costs $\$7225$. To get a sequence which takes lesser time, we must look for
alternative modes of transport which are faster but not much more expensive. We cannot
replace any of the non-air routes by air routes, as that would overshoot the budget. Thus, the
only possibility is changing the mode of transport from London to istanbul from road to rail.
However, if Balaji travels by rail on all three routes, that would cost $\$305$ more. So he travels by
rail on only two routes (Paris to Vienna to Istanbul) and by road from London to Paris. For all
other routes, he travels by air, except San Francisco to New York City where he travels by rail.
This sequence would take 151 hours and cost $\$7490$.