What electric field is needed in order to produce zero deflection of an electron with an initial speed of v = 4.0×106 m/s in a magnetic field of 12 mT perpendicular to the electron’s motion? Sketch the system, including appropriate ~E, ~B, and ~v vectors

what is the question?

i had this question and the answer was 3.15 miles.

martina travels from school to her mom's office. from there, she walks to school. after school, she walks to the library and then to a friends house before finally ending back at home. find martina's total distance traveled.

a) 0 miles  

b) 0.4 miles  

c) 1 mile  

d) 3.15 miles