James can do a farmer's walk with 300 pounds per hand for 20 meters.  He can lift 30% more if he only goes 10 meters.  In addition, lifting straps give him another 20%.  How much can he move with lifting straps for 10 meters if he increases his 20-meter distance without straps by 50 pounds and everything else increases in proportion?
After the increase, he can lift 300+50=<T>add(300, 50)=350 pounds
Decreasing the distance increase the amount he can lift by 350*.3=<T>multiply(350, 0.3)=105.0 pounds
So he can lift 350+105=<T>add(350, 105)=455 for 10 feet
The straps add another 455*.2=<T>multiply(455, 0.2)=91.0 pounds
So his total weight is 455+91=<T>add(455, 91)=546 pounds per hand
