Please answer the following questions

(a). A system of six linear equations with five unknowns r1, T2, 13, I4, Is has two solutions ($1, 12, 13, TA, 15) = (1, 2,3, 4, 5) and (T1, 12, 13, TA, X5) = (7, 8,9, 10, 11) . Find a solution (21, 12, r3, ma, ;) of this system such that r, = 19. [Marks= 5] (b). Three points A. B, C in R are given: A = (1, 2,3), B = (2,2, -1), C= (3, 1,0). Find the coordinates of the point D lying on the line passing through A and B such that the vector CD is orthogonal to the vector AB. [Marks= 5]