Change percentage via an Option button

I am working in a spreadsheet that prices products.
in cell(E2) is an option button that selects a mark up of 20%(has value of 1)...under format control,,, cell link is $E$2
in cell(E3)I have altered formula in (P5) to +IF(E2 =1.0.20,0.25,0.15) but this does not work, it comes up with pop up window "You've entered too many arguments for this function"

any help I would be grateful

Try

-IF(E2=1,0.2,IF(E3=1,0.25,0.15))

Alternatively, you could use

=E2*0.20 + E3*0.25 + E4*0.15

Alternatively alternatively, you could use

[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]=SUMPRODUCT(E2:E4,{0.2;0.25;0.15})

[SUB][SUP]
[/SUP][/SUB][/FONT]