formula help

Hi,

I'm looking to create a formula where the sum depends on the number entered in the first cell,

for example the 1st variable can be 1-2, 2nd is 3-4 and 3rd is 5+.   

If the first variable is 1-2 then hours worked should be multiplied by 5,

if the 1st variable is 3 or 4 then ours worked should be multiplied by 7.5,

if its 5 or more then its ours worked multiplied by 10

In the example below the 1st answer would be 15 and the 2nd would be 30.

Hope that makes sense!