Just starting out and out of shape, 1.5h sounds to little. Two hours sounds more like it. But it really depends a lot on the kind of bike that you have. I can be twice as fast on the good road bike than on the x-mart mountain bike.

You'll need a bike odometer if you don't have one already. Calculate how slow can you be allowed to go for the time you have. For 14Mi in 1.5H you could not go slower than 9.3Mph. And that does not take into account stops at traffic lights and rest stops. When I started biking, anything above 7Mph was pretty hard.

And the often overlooked detail... is your saddle comfortable enough for a 14mi/2h trip?