calculate_mobile_bill

incluging 2 part of programming

1. input file 'promotion1.log' including 'date', 'startTime', 'endTime', 'phoneNo', and 'promotion'to calculate difference between start time and end time , calculate total amount due for each phone number, and write phoneNo and total amount due to file 'promotion1.json' (output and sourecode have shown in folder 'CalculatePromotion')

2. build webpage using react.js to input file 'promotion1.json' (from 1.) to show on http://localhost:3000/ (output and sourcecode have shown in folder 'show-bill-price')