public static void main(String[] args) {
		try {
			BufferedReader br = new BufferedReader(new InputStreamReader(
					System.in));
			String[] firstLine = br.readLine().split("\\s+");

			int n = Integer.parseInt(firstLine[0]);
			double p = Double.parseDouble(firstLine[1]);
			double r = Double.parseDouble(firstLine[2]) / 100.0 + 1.0;
			Node[] nodes = new Node[n];
			for (int i = 0; i < n; i++) {
				nodes[i] = new Node(i);
			}

			for (int i = 0; i < n; i++) {
				String[] line = br.readLine().split("\\s+");
				int m = Integer.parseInt(line[0]);
				if (m == 0) {
					nodes[i].num = Integer.parseInt(line[1]);
				} else {
					for (int j = 0; j < m; j++) {
						int y = Integer.parseInt(line[j + 1]);
						nodes[y].parent = nodes[i];
					}
				}
			}
			nodes[0].price = p;
			double sum = 0.0;
			for (int i = 0; i < n; i++) {
				if (nodes[i].num > 0) {
					double price = price(nodes[i], r);
					sum += price * nodes[i].num;

				}
			}

			System.out.println(String.format("%.1f", sum));
		} catch (Exception ex) {
			throw new RuntimeException(ex);
		}
	}