Calculation with JSON [on hold]

I want to write simple program to calculate balance amount from the JSON object.

Below is my JSON object

[
  {name:"12345",dramt:30000, cramt:70000},
  {name:"abcd123",dramt:20000, cramt:75000},
  {name:"abcd123",dramt:40000, cramt:100000},
]

Formula to calculate balance = cramt - dramt

Thanks a lot