Answer
The person could hold a mass of 7.0kg
Work Step by Step
We sum the torques about the elbow joint to solve for the mass the person can hold. Therefore;
$(+ \circlearrowleft) \sum \tau=0$
$.060m*450N-0.15m*2.0kg*g-.35m*5.0kg*g=0$
$m=\frac{.060m*450N-.15m*2.0kg*g}{.35m*g}$
$m=\frac{.060m*450N-.15m*2.0kg*9.8m/s^2}{.35m*9.8m/s^2}$
$m=7.0kg$
Therefore, the person could hold a mass of 7.0kg.