How does a concave mirror form an image?

What defines the mass number of an isotope? a. the sum of the neutrons and protons b. the sum of the neutrons and electrons c. the number of neutrons d. the number of protons

Aparticle with mass 1.81×10−3 kg and a charge of 1.22×10−8 c has, at a given instant, a velocity v⃗ =(3.00×104m/s)j^. what are the magnitude and direction of the particle’s acceleration produced by a uniform magnetic field b⃗ =(1.63t)i^+(0.980t)j^?

Could someone . i have tried to solve myself but my calculation is off