B) For the setting, we need to update you the price difference because of the center stone change.
It is $718 for this ring semi mount without#2.36ct center,with 4 pieces 1.5×3mm marquise lab grown diamond and no bigger than 2.5mm round lab grown diamond in 10k white gold.In #28570, you need to pay the price difference $78.14($718-$639.86).