An oil company is plaining to drill three wells in an rural area of central Punjab. One Part used in drilling is constantly under stress and has a breakage for eight wells drilled. Break occurs at random and without regard of the length of time the part has been in use to avoid having send back for additional part , they wish to take along any replacement parts that will be needed, on the other hand any parts not used will be discarded at the side. How many extras parts (in addition to the one already in drilled) should be taken so that the probability of having to send back for the parts is L/100+0.05.

where L=6