I have selected 'Free Shipping' as a shipping option of the settings page in my wordpress. But considering that most buyers use epacket services, I need to know whether the 'free shipping' is convenient or epacket? The epacket option states the cost can range from 0-$4.5. How then will I know which products of mine will have 0 cost and which ones going till $4.5? If I put $0 in the cost bar for epacket option, will the 'free shipping' become unnecessary since both are FREE but only the epacket with faster delivery?