Who pays how: payment method share

Finance is renegotiating processing fees with payment providers and needs to know how much of the money flows through each method. The payments table holds one row per payment; an order can be split over two payments (for example a Gift Card plus a Card). Cancelled orders have no payments.

Task: for each method return method, revenue (sum of amount, ROUND(x, 2)) and pct_of_total (its share of the total amount over all payments, in percent, ROUND(x, 2)). Sort by revenue from high to low, then by method A to Z.