General ACCAFA1(fia) Payroll problem on Exam kit.

An employee earns $24,000 per annum. In May a salary increase was agreed to $26,000 pa, which was backdated to 1st April.In addition, a 2% bonus of basic monthly salary is payable if the company profits exceed a certain figure.The profit threshold was passed for May. Calculate the employee's gross earnings for May. A. $2,244 B.$ 2,444 C.$2040 D. $2,440 My main problematic word is backdated.How does it work? Another word is threshold. What does it mean? Please explain elaborately.Thank you.