Short Sight Limited is an optometry clinic that is GST registered on a invoice basis. Short Sight sells a customer a pair of glasses on 28th March 2017 at a price of $759 including GST. The customer pays a deposit on that date of $115 and the balance of $644 on 15 April 2017 when the glasses are made up and the customer takes them home. How should Short Sight Limited return the GST on the sale?

a) $99 in the return covering the period including 28th March.

b) $15 in the return relating to 28th March and $84 in the return relating to 15th April.

c) No return of GST is required as the supply is exempt.

d) $99 in the return covering the period including 15th April.