Number 28 please

28. Which of the following are always true, and which are not always true? Give reasons for your answers. E a. u . v = v . u b. uXv = -(vxu) C. (-u) XV = -(ux v) d. (cu) . v = u . (cv) = c(u . v) (any number c) e. c(u X v) = (cu) X v = u X (cv) (any number c) f. u . u = u2 g. (u xu) . u = 0