Fixed. Variable Total cost functions cly)is the total cost of all inputs, fixed and variable, when producing y output units. cly)is the firm's total cost function c(y)=F+Cy(y)Fixed, Variable & Total Cost Functions c(y) is the total cost of all inputs, fixed and variable, when producing y output units. c(y) is the firm’s total cost function; c(y) = F + cv (y)