Hello , I am having trouble with the following question:

The answer is supposed to be 30 but i am getting 33.75Tom and bill agreed to race across 50-foot pool and back again.They started together but Tom finished 10feet ahead of bill.IF there rates were constant and Tom finished the race in 27 seconds , how did it take bill to finish:

Here is how i am doing it:

Toms velocity is: 50/27 ft/sec

Bills velocity will be : 40/27 (Because Tom finished 10ft ahead of Bill)

So Time taken for bill to finish the race will be:

S/V = 50 / (50/27) = 33.75

Could anyone tell me what i am missing or doing wrong!! Thanks