Can anybody help with this
Products sell at a discount - bigger order = bigger discount
Number Cost
5 £1.50
10 £1.25
15 £1.20
20 £1.00

To buy 12 the breakdown would be:
1st 5 @ £1.50=£7.50
2nd 5 @ £1.25=£6.25
Last 2 @ £1.20= £2.40

What I want to be able to do is type in the number wanted in cell A1 & then
B1 would give me the answer £16.50

I hope this can be sorted with a formula

Thanks
Saintsman