Jack borrows $A, over 15 months, at interest of 12% compounded monthly: 1% per month.

For the first 5 months, payment will be 10% of balance owing.

As example, if $3000 borrowed, 1st payment will be $300,

resulting in balance owing of 3000 - 300 + 30 = 2730;

so the next payment will be .10(2730) = $273,

resulting in balance owing of 2730 - 273 + 27.30 = 2484.30

For the remaining 10 months, the monthly payment will be constant

at $50 per month: the 10th $50 payment will result in a zero balance owing.

How much did Jack borrow?