Answer
(a) $9.99~kg$
(b) $98.0~N$
Work Step by Step
The positive $y$ axis points upward.
$g=9.81~m/s^2$
$F=105~N$, upward
$W=mg=m(9.81~m/s^2)$, downward
(a) $F_{net}=ma_y=m(0.705~m/s^2)$, also: $F_{net}=F-W$. So:
$F-W=m(0.705~m/s^2)$
$105~N-m(9.81~m/s^2)=m(0.705~m/s^2)$
$105~N=m(10.515~m/s^2)$
$m=\frac{105~N}{10.515~m/s^2}=9.99~kg$
(b) $W=mg=(9.99~kg)(9.81~m/s^2)=98.0~N$
