sales percentage lookup

I have a formula that calculates a sales percentage based on the amount of sales, I cannot make it work any help.
=IF(B9<1000,($B$3*5/100),0*OR(B9<999.99,,($B$3*10/100),0*OR(B9>3999.99,,($B$3*12.5/1
the forumala is supposed to calculate anything from Cell B3, if less than $1000.00 then multiply by 5%, if between $1000.00 to $3999.99 then mulitply by 10% and if over $3999.99 then multiply by 12.5%.