Topic on game theory

Jimmy is living alone. Every week he buys a list of groceries from a local wet market where he can bargain for a lower price. Unfortunately, he is ill and unable to walk out of his house recently. He finds one helper online. Jimmy signs a contract with the helper. Jimmy will give $10 each time to the helper for buying a list of groceries from the wet market using Jimmy's credit card. Is the contract a "cost-plus contract" or "fixed-price contract"? Indicate the contract type and explain your