Answer
(a) negatively charged
(b) $1.5u$
Work Step by Step
(a) We known that the charged particle enters to the right in the given magnetic field and the path of the charged particle is circular. Hence, by the right hand rule, the direction of the magnetic force will be towards the right. This is only possible if the charge is negative.
(b) We can find the required mass of the particle as follows:
$F=evB$
$\implies \frac{mv^2}{r}=evB$
$\implies m=\frac{Ber}{v}$
We plug in the known values to obtain:
$m=\frac{(0.180T)(1.6\times 10^{-19}C)(0.520m)}{6.0\times 10^6m/s}$
$m=2.496\times 10^{-27}Kg$
$m=(2.496\times 10^{-27}Kg)(\frac{1u}{1.67\times 10^{-27}Kg})$
$m=1.5u$
