Tony Stark grows pumpkins. If Tony plants no seeds on his farm, he gets no harvest. If he plants $1$ bag of seeds, he gets $400$ pumpkins. If he plants $2$ bags, he gets $700$ pumpkins. If he plants $3$ bags, he gets $850$ pumpkins. A bag of seeds costs $$100,$ and seeds are his only cost. Tony's production function exhibits

increasing marginal product

none of these

constant marginal product

decreasing marginal product