In which case did the taxpayer derive assessable income during the year ended 30 June 2020?

	a.	Fridge World sells refrigerators. On 30 June 2020, it sells a refrigerator for $2,000. The customer enters into a lay-by arrangement by paying an initial deposit of $400. For the next four weeks, the customer continues to make $400 payments until the final $200 instalment is paid on 2 August 2020;
	b.	Learn to Dance is a dancing school. On 30 June 2020, it receives a non-refundable upfront payment of $150 from a customer for 3 dancing lessons (ie. $50 each). The three dance lessons are conducted on 6 July, 13 July and 20 July 2020;
	c.	Malik received a $10,000 bonus from his employer on 12 July 2020 in appreciation of his hard work for the year ended 30 June 2020;
	d.	Julie, a chartered accountant practicing as a sole practitioner, invoiced some clients $12,000 on 30 June 2020 for services provided up to that date. Julie received this amount in the mail on 10 July 2020.