How do you solve these?

1. If vector a = (3, 2, 9), and b = (-4, 7, 2), find a x b. 2. For any vector a find a x a . Explain why. 3. a. Explain why the cross product does not exist in 2 - space. b. How could you do a cross product with two dimensional vectors? 4. The magnetic force ( F M)on a particle in a magnetic field is found by FM = / x B, 7 is the charge multiplied by the velocity of a charged particle and ? the strength of the magnetic field, in Tesla (T). An electron accelerates from rest to the right, in a horizontally directed electric field. The electron then leaves the electric field at a speed of 4.0 x 106, entering a magnetic field of magnitude 0.20 T (Tesla) directed into the screen. Calculate the magnitude and direction of the magnetic force on the electron. (Charge on an electron: q = 1.6 x 10-19)