This is for an assignment

on my income statement the purchases for the year are £30,000 (energy drink 20p (manufacturing costs) x 150,000 cans (projected sales)
the cost of sales are 45% of the sales (£120,000) so this is £54,000.

so, the purchases = £30,000 and the cost of sales = £54,000 how is it this? Do these figures make sense?

I know need to to know how can I work out the closing inventory now, I can't seem to get to the closing inventory because the cost of sales is bigger than the purchases. Im confused. Can anyone help please?

thanks