Calculate Amount Paid in Taxes

You are given a 0-indexed 2D integer array brackets where brackets[i] = [upper_i, percent_i] means that the i^th tax bracket has an upper bound of upper_i and is taxed at a rate of percent_i. The brackets are sorted by upper bound (i.e., upper_{i-1} < upper_i for 0 < i < brackets.length).

Tax is calculated as follows:

• The first upper_0 dollars earned are taxed at a rate of percent_0.
• The next upper_1 - upper_0 dollars earned are taxed at a rate of percent_1.
• The next upper_2 - upper_1 dollars earned are taxed at a rate of percent_2.
• And so on.

You are given an integer income representing the amount of money you earned. Return the amount of money that you have to pay in taxes. Answers within 10^-5 of the actual answer will be accepted.