Combine Shipping Rates

If there are multiple vendors with their own shipping rates, Garnet Marketplace will display at most two rates:

1. the sum of the cheapest rate,
2. the sum of the fastest rate.

Here is the combined rate of a flat rate from the first vendor and the live rates from the second vendor.

Unfortunately, Shopify does not allow the customer to select one shipping per items (link) so we have to aggregate the rates.

Combine rates ETA is computed by taking the maximum of both rates. If the first rate has a delivery window of 1 to 3 days, and the second one 2 to 5 days, then the combine rate will be 3 to 5 days.