Total `= .^100 C_40`
(a) no of ways such that `A,B in 40 => .^98C_38`
`AB in 60 , => .^98C_40`
p(A & B together) `= (.^98C_38 + .^98C_40)/(.^100C_40)`
(b) p(A,b in different) `= 1 - (.^98C_38 + .^98C_40)/(.^100C_40)`
` = 2(.^98 C_39)/(.^100C_40)`
answer