An artillery target may be either at point I with probability 8/9 or at point II with probability 1/9 we have 55 shells, each of which can be fired either rat point I or II. Each shell may hit the target, independent of the other shells, with probability 1/2. Maximum number of shells must be fired a point I to have maximum probability is `20` b. `25` c. `29` d. `35`