Beginning of Esha time

Q: I read that Maghrib prayer time ends when the redness in the sky goes away. Also I read that it ends half an hour before Isha Azan. Which one is true? Half an hour before Isha azan I feel the sky becomes darker. Can I still pray Maghrib or should I mention as qadha namaz? As I'm a working woman and gets little late to reach home and can't pray in van.

Travelling with a non-mahram

Q:

1. Is it permissible for a woman to sit in the passenger seat of a car which is being driven by a non mahram man?

2. Is it permissible for a woman to sit behind a non mahram man on a motorbike or bicycle?

3. Is it permissible for a non mahram man and a non mahram woman to sit next to each other?

Marking items at a higher price due to people asking for discounts

Q: Someone owns a shop. Because people often ask for discounts, they mark the items higher, so when people ask for discounts, they give it and still get their desired profit. 

Eg. He wants a profit of R50 for a R100 item. However, knowing that people will ask for a discount, he marks the item as R200. So when people ask for a R50 discount, he gives it to them and still gets his desired profit. Is this permissible in Shari'ah or is that money haraam?