Banker's Discount - General Questions

What is the banker's discount on a bill of Rs. 8,700 due 3 months hence at 6% per annum?

The true discount on a bill due 3 year(s) hence at 12% per annum is Rs. 1,764. What is the banker's gain?

The true discount on a bill due 1 year(s) hence at 15% per annum is Rs. 750. What is the banker's gain?

The banker's discount on a sum is Rs. 57.75 and the true discount is Rs. 55. What is the sum due?

The banker's discount on a sum is Rs. 1,287 and the true discount is Rs. 990. What is the sum due?