In the sixth power of (a + 2b-3c), find: (1) the coefficient of AB squared C cubic and (2) the sum of all the coefficients with a cubic term Thank you very much~

In the sixth power of (a + 2b-3c), find: (1) the coefficient of AB squared C cubic and (2) the sum of all the coefficients with a cubic term Thank you very much~

1) In (a + 2b-3c) ^ 6, one bracket takes a, two brackets take B, and three brackets take C
Coefficient = C (6,1) * C (5,2) * C (3,3) * 2 ^ 2 * (- 3) ^ 3 = 6 * 10 * 1 * 4 * (- 27) = - 6480
2) When the sum of all coefficients with a ^ 3 is equal to B = C = 1, the coefficients of a ^ 3 in (A-1) ^ 6 expansion,
Therefore, the coefficient = C (6,3) (- 1) ^ 3 = - 20