Oh and chatty cathy cell phone plan she pays four minutes used plus a fixed monthly charge for 500 minutes she pays $35 total and for 1500 minutes used she pays $55 total

So is it saying what is the monthly fixation charge ? if it is the answer would be if it's 500 minutes for $5 so fixed cost would be $30
cost = $30 + $5 * the number of mins divided by 500
Hope this helps

It is the top one. the answer is -7. that is smallest

Yes you do, so £1973.09 - £1473.50 = £499.59 so tim overpaid £499.59 .hope this ; )