I need some help:

An electron follows a helical path in a uniform magnetic field given by B= (21 i - 57 j - 28 k) mT. At time t = 0, the electron's velocity is given by v = (21 i - 33 j + 44 k) m/s. (a) What is the angle between v and B? The electron's velocity changes with time. (b) Do its speed changes with time? (c) Do its angle changes with time? (d) What is the radius of the helical path?