function book_keisan() {
	    var bf = document.book_total;
		
		var arr = [bf.hg_n,bf.g_n,bf.b_n,bf.hb_n,bf.t5_n,bf.t10_n];
	    var totalbook = 0;
		
		for (var i in arr) {
			
			if (NumberCheck(arr[i])) {
				totalbook += parseFloat(TranceBook(arr[i].value,i));
			}
		}
		
		updateTotal(totalbook);
	}
	
	function TranceBook(v,pos) {
		if (pos == 0 || pos == 3) {
			v*=0.5;
		} else if (pos == 5) {
			v*=2;
		}
		
		return v;
	}
	
	function NumberCheck(obj) {
	    var v = obj.value;
		
		if(v.match(/[^0-9]+/) || !v) {
			v = "";
			return false;
		} else {
			return true;
		}
	}
	
	function updateTotal(total) {
		document.book_total.total_book.value = total;
	}
	
	function bookClear() {
		document.book_total.hg_n.value = 0;
		document.book_total.g_n.value = 0;
		document.book_total.b_n.value = 0;
		document.book_total.hb_n.value = 0;
		document.book_total.t5_n.value = 0;
		document.book_total.t10_n.value = 0;
		document.book_total.total_book.value = 0;
	}