How to set a 'Or' formula

I have a cell that can read either 'standard' or a value. (A3)
The next cell needs to calculate a length depending on what cell (A3) reads.
This will be 2* cell (A3)'s value, or if cell (A3) reads 'standard' it must cell (A2)*0.66*2

What should the formula read?

Thanks in advance!

Thank you! Perfect answer. All working!!.