Capital structure and finance costs

At 30 June 20X2 a company had $1m 8% loan notes in issue, interest being paid half-yearly on
30 June and 31 December.

On 30 September 20X2 the company redeemed $250,000 of these loan notes at par, paying interest due to that date.

On 1 April 20X3 the company issued $500,000 7% loan notes, interest payable half-yearly on
31 March and 30 September.

What figure should appear in the company’s statement of profit or loss for interest payable in the year ended 30 June 20X3?

13.8 $73,750
July – September 1,000,000 * 8% * 3/12 = 20,000
October – March 750,000 * 8% * 6/12 =30,000
April – June 750,000 * 8% * 3/12 =15,000
500,000 * 7% * 3/12 = 8,750
73,750
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I don’t understand why they do 3 months calculation, July – September 1,000,000 * 8% * 3/12 = 20,000
Can you please explain sir