I understand that if PED = (-)0.625, this means price and quantity are inversely related. So an increase in quantity (to 300,000 units) would require a fall in price. -0.625 is also inelastic.
I've also tried to backwork the PED equation to get this: % change in demand (50) / % change in price (-80) = PED (-0.625). But I'm not sure how I should be using the -0.625 here or if I really understand what the question is getting at.
If it's just a question of meeting the original sales revenue (200,000 x £10 = £2 million). Then 2m / 300,000 = £6.66666, so to achieve at least £2m, 300,000 would have to be sold at £6.67. But that doesn't factor in the -0.625 PED, so I think I'm lost!