Jack is filling his new six person hot tub with a water hose. After 58 minutes, his hot tub has 318 gallons water. His hot tub holds 1,360 gallons of water. He adds another water hose that flows 50% faster. Find the constant of proportionality for the flow rate of the two water hoses combined? (round to nearest tenth)
A) 6.9
B) 8.2
C) 13.7
D) 16.4