My 2018 1.4TSi (150) has averaged 45mpg. How far I can drive on a full tank depends on how close I am prepared to go to empty. Cost depends on how empty the tank is when I fill it and the price where I fill it up.
Surely all you need to know is average mpg for your type of driving and that the tank holds 45 litres (9.9 gallons) - now do your own calculations.
Although mine isn't an fr I have the same engine. My trip computer shows me averaging 48mpg.
I tend to get get between 450-500 miles from a tank and use either tesco momentum 99 or standard esso most the time.
The most I have got is 515.
I'm pretty sure they hold 50 litres of fuel.
If you are driving predominently in the city, you can expect 35-40mpg..highways approx 55mpg (or more depending on gradient) @ NSL So you can expect anything from 380-530 miles from a tank from full to when the red light comes on.