I want to have 3 conditions, most important is the "Yes" condition.  Line 1 or 2don't work, but 3 does, but I don't have the "Yes" condition in example 3.  How do I write the string?

1.  if (((input.Billed  !=  0.0)  &&  (input.Invoice_Email  !=  null))  &&  (input.Resend_Invoice_Email  ==  "Yes")))

3.  if ((input.Billed  !=  0.0)  &&  (input.Invoice_Email  !=  null))