Hi Answer to each option is given as:
a) 122,523,030
b) 72,930,375
c) 223,149,655
d) 100,626,625
And I used the following approach to each option but answers don't match.
a) C(5,1)*C(21,5)*6!
b) C(5,2)*C(21,4)*6!
c) P(26,6)-P(21,6)
d) [C(5,2)*C(21,4)+C(5,3)*C(21,3)+C(5,4)*C(21,2)+C(5,5)*C(21,1)]*6!
Please check.