So, I'm not a developer at all, and I'm making an interactive map. I feel like I'm very close, but there's one thing that I can't figure out. When I hover the mouse over a U.S. state, I'd like the numerical value to be formatted to include a dollar sign. Here's my map code, could someone please tell me what I'm doing wrong? Thank you!

function drawVisualization() {
  var data = google.visualization.arrayToDataTable([
    ['State', 'Foo Factor'],
    ['US-IL', 200],
    ['US-IN', 300],
    ['US-IA', 20],
    ['US-RI', 150]
  var currency_formatter = new google.visualization.NumberFormat({prefix: '$'});
  currency_formatter.format(data, 2);
  var geochart = new google.visualization.GeoChart(
  geochart.draw(data, {width: 556, height: 347, region: "US", resolution: "provinces"});