BTW, a 737 is rarely, if ever, flown at those altitudes you mentioned - too low. Economy flight is possible only at very high 20 thousands and 30 thousands. Although here in Europe A320s and B737 sometimes, or often, get talked by control into using flight levels in the mid 20 thousands, due to traffic situations. But airlines don't like that, it costs them more fuel.
For your flight, it is around 250 miles, maybe 45 minutes. FL 260-300 probably would be adequate. I do flights of that length at those altitudes at least.
In your country, I think the altitude for Victor Airways (low altitude airways) is below and for Jet Airways (high altitude airways) is above 18000 feet.
