First you would need to find the total cost for just one fill-up...
$1.95(price per gallon)*210(how many gallons the tank will hold) =$409.5 (for one fill-up)
Now to find the price for 6 fill-ups...
$409.5(for one fill-up)*6(Total number of fill-ups) =$2,457 (for 6 fill-ups)
So your answer would be $2,457
Hope this helps! :)