Shoppers at Retailer R who purchased substitute items from other manufacturers on DayI paid a total amount that was approximately 78 of the total shoppers would have paid had each of them been able to purchase ProductXon Day 1. “was 和 would have paid ”都在一个从句里，怎末会有两个谓语动词？“had each of them been able to...”这部分是跟谁啊？看不懂