function hyouka(){

var form = document.form_hyouka;

form.elements["yoi"].value = eval(form.elements["c100"].value) + eval(form.elements["c200"].value);

form.elements["warui"].value = eval(form.elements["c400"].value) + eval(form.elements["c500"].value);

form.elements["goukei"].value = eval(form.elements["yoi"].value) - eval(form.elements["warui"].value);

}