There was increase in tax rate from 20% to 24% w.e.f. 1.09.2019. Which of the following rate isapplicable when services are provided after change in rate of tax in September 2019, but invoice issued and payment received, both in August, 2019 :

• A. 20% as it is lower of the two
• B. 24% as it is higher of the two
• C. 20% as invoice and payment were received prior to rate change
• D. 24% as the supply was completed after rate change