$5.)$ a$)(5$ points$)$ What magnitude and direction of electric field is required to make a particle with a positive charge travel in a straight line in a magnetic field vec$(B)=0\mathrm{.}08$That$(k)$ if and only if it is going at a velocity $v=4000\frac{(m)}{(s)}$hat$()?$

b$)(5$ points$)$ If the particle has a charge $|q_e|$ and travels in a circle of radius $R=0\mathrm{.}00125$ m after leaving the region with the electric field you calculated above $($still being exposed to the same magnetic field$),$ what is the mass of the particle?