Help with formula

`Please help me to create a formula.

The configuration of the form is as follows:

<strong>field name11</strong>
It is a checkbox with text option, and with value option.
If the checkbox (fieldname11) is selected, it shows another additional checkbox (fieldname12)

<strong>field name12</strong>
The “fieldname12” checkbox has 3 options, with three different numerical values ??(0.38954286, 0.47950002 and 0.51950004).

<strong>field name 6</strong>
It is an editable number, for the user to enter an amount (for example: €500)

<strong>field name9 </strong>
is the calculated field

I need to generate the following formula in Calculated Field Form:

fieldname9 = fieldname12 x fieldname 6 (<strong>according to the selected value</strong>) + 1.19

Thank you very much.