Charles has decided to open a lawn-mowing company. To do so, he purchases mowing equipment for $, buys gasoline ($ in gas is required to mow each yard), and pays a helper $ per yard. Prior to opening the lawn company, Charles earned $ as a lifeguard at the neighborhood swimming pool. Assume the money he used to purchase the mowing equipment could otherwise have earned percent per year in the bank and that the mowing equipment depreciates at percent per year. Charles plans to mow yards per year. What is Charles's implicit costLOADING... of production? Charles's implicit cost of production is $ nothing per year. (Enter your response as an integer.)