sagarmatha this question hardly takes 5 minutes to do  for the student of probablity and you are saying you have no time. I am not the expert on probablity and I may be wrong as well.  but Here is the answer I think.


P1 = 0.35......probablity of using coupon

P2=  0.65 not using a coupan


1.  question  ......... Exactly 3 uses coupon


3C10*(0.35) power 3  (0.65) power 7 =0.25

2. question  nine or more used coupon


9c10* (0.35) power 9 * (0.65) power 1 +10C10*(0.35)power10