The total force is the Lorentz force, given by the following. F = qE + qvector v × B = q E + vector v × B We substitute the unit-vector coefficients given above and use the following rules for multiplying unit vectors in a cross product. î × î = ĵ × ĵ = k × k = 0 î × ĵ = −ĵ × î = k ĵ × k = −k × ĵ = î k × î = −î × k = ĵ (a) After substituting and combining the resulting coefficients according to the rules above, we have the following. F = 3.2 × 10−19 C î − ĵ + k N/C = î − ĵ + k × 10−18 N