The probability of an integrated circuit passing a quality test is 0.86. In a batch of 10 integrated circuits, find the probability that


iii) at least 2 will fail
iv) fewer than 2 will fail


I know the forumula to use

P(x) = NCr (a)^r (b)^r-1

but when it gets "least" and "fewer" i start to get confused
whats the easy to this i know its 1 - p(something) but not really sure

Help please guys