Selling electricity from a vending machine

Q: I would like to find out the following:

If one has to sell electricity from a vending machine, the service provider gives you a discount of 1, 5% on the sale of the electricity.  Can one charge a customer and additional 5% on the sale of the electricity {e.g.: a customer comes to buy electricity from you for R20-00 but you charge him R21-00 for the sale.  On the customer’s slip they will see that they have only purchased electricity for R20-00.) The cost incurred by me is that I will have to pay the cash deposit fee of about 1%, a monthly unit rental fee of about R150 per month. Is it permissible to do this type of a sale?

Arabic TV series show Jews fighting alongside the Muslims in the battle of Badr

Q: In the Arabic TV series about Omar Ibn Al Khattab, a Jew is shown fighting along with the Muslims in the battle of Badr. Is there evidence for this having happened in reality - did a few Jews participate on the Muslim side in the battles of Badr and Uhud (i.e. without first having converted to Islam)?