Thanks mbcx - there guys - see? I told you it was straightforward.
Kind of depends where you are.
For me, at 300kts 'tacho', I would be happy at 10,000' at 40nm. You need about 3 miles/1000' with 300 and -20, so at 30 miles you would be around 7000' if you maintained 300kts. Target (still air) is ballpark 30nm at 10,000 ft/250kts for a throttle closed to 210kts at 10 miles. Maintaining 300 to level-off (3000'?) needs another 12 miles, leaving you at 18nm from touchdown at 3000'/300kts - easy! You never know, you might also please Rainboe with a perfect CDA! One would also expect the -20 to reduce on the way down too if you are landing straight-in or it is time to whinge about a runway change
Of course I'm sure Olen is also aware of descent rate restrictions relating to MSA which may also affect his speed?