Mrs. Moldovan operates a soybean farm. She buys many supplies in bulk. Often the bulk products need to be custom mixed before Mrs. Moldovan can use them. To apply herbicide to a large field she must mix a solution of 67% herbicide with a solution of 46% herbicide to form 42 liters of a 55% solution. Which system of equations could be used to determine the amount of each solution Mrs. Moldovan needs to use to make the final solution? Let x = the number of liters of 67% herbicide and y = the number of liters of 46% herbicide.