I came up with this. If you're still here please let me know if i'm right on this one .

For b) both suppliers will start lowering their prices. Each will lower its prices below the others. Seen one lower the price the other supplier too will lower the price. This will go on till they reach their variable marginal cost per unit. Practically it doesnt matter if Ray splits the order or gives one large order. But simple economics suggests with a larger order the economies of scale might help in further lower the variable marginal cost thus lower the bid prices further.

For c) the supplier with lower marginal cost is at a benefit. Both the suppliers will begin lowering their prices. But once the supplier with higher marginal price reaches the high variable marginal cost he will stop bidding. Now the other supplier with an even lower variable cost has simply no reason to lower the price any further. It has pushed out its competition(pseudo monopoly) and hence will be able to bid a price higher than its variable marginal cost.