Question 370763
t = d / r ___ the upstream time is 1/3 h (20 min) longer


5 / (b - 4) = [5 / (b + 4)] + (1/3)


multiplying by 3(b-4)(b+4) ___ 15b + 60 = 15b - 60 + b^2 - 16


b^2 - 136 = 0