title: Simple currency conversion function
body: <p>I can't figure out why my USD total won't print correctly. All I would like is for the user's input to be multiplied by 0.73 and print usd_total.</p>
  
  <p>I am getting this error:</p>
  
  <p>usd_total = aus_to_us(us_exchange * aud_amount)
  TypeError: aus_to_us() missing 1 required positional argument: 'aud'</p>
  
  <pre><code>def aus_to_us(exchange_rate, aud):
      usdConversion = exchange_rate * aud
      return usdConversion
  
  aud_amount = float(input('Enter the amount in AUD: '))
  us_exchange = 0.73
  usd_total = aus_to_us(us_exchange * aud_amount)
  print('The amount in USD is: ', usd_total)
  </code></pre>