I know the correct answer is the one highlighted, but I need an explanation as to why, I'm just not understanding

IU V/IVI SUPPOSE LIaLa TIHIS WIAILUSE VI PIVUUCITY... Suppose that a firm's total cost of producing an output of 400 units a day is currently $2,000 If technology and the price of inputs remain unchanged, what level of output would be produced if total cost rises to $4,000 and diseconomies of scale exist? Multiple Choice O 5 units ices More than 400 but less than 800 units O 800 units More than 800 units