Scenario 13-7 Farmer Jack Is a Watermelon Farmer.If Jack Plants No Seeds

Scenario 13-7
Farmer Jack is a watermelon farmer.If Jack plants no seeds on his farm,he gets no harvest.If he plants 1 bag of seeds,he gets 30 watermelons.If he plants 2 bags of seeds,he gets 50 watermelons.If he plants 3 bags of seeds he gets 60 watermelons.A bag of seeds costs $100,and the costs of seeds are his only costs.
-Refer to Scenario 13-7.What is the shape of Farmer Jack's marginal cost curve?

A) upward sloping
B) downward sloping
C) first upward sloping,then downward sloping
D) constant