Given that $$x$$ is a random variable in the range $$\left[ {0,\infty } \right]$$ with a probability density function $${{{e^{ - {x \over 2}}}} \over K},$$ the value of the constant $$K$$ is _______

The figure shown the schematic of a production process with machines $$A, B$$ and $$C.$$ An input job needs to be pre-processed either by $$A$$ or by $$B$$ before it is fed to $$C,$$ from which the final finished product comes out. The probabilities of failure of the machines are given as:
$${P_{\rm A}} = 0.15,\,\,{P_{\rm B}} = 0.05\,\,\& \,\,{P_C} = 0.1$$

Assuming independence of failures of the machines, the probability that a given job is successfully processed (up to the third decimal place) is _____.

A fair coin is tossed till a head appears for the first time. The probability that the number of required tosses is odd, is

The box $$1$$ contains chips numbered $$3, 6, 9,$$ $$12$$ and $$15$$. The box $$2$$ contains chips numbered $$6, 11, 16, 21$$ and $$26$$. Two chips, one from each box are drawn at random. The numbers written on these chips are multiplied. The probability for the product to be an even number is ______________.