A hydraulic structure has four gates which operate independently. The probability of failure of each gate is $$0.2.$$ Given that gate $$1$$ has failed, the probability that both gates $$2$$ and $$3$$ will fail is

A delayed unit step function is defined as $$$u\left( {t - a} \right) = \left\{ {\matrix{ {0,} & {t < a} \cr {1,} & {t \ge a} \cr } } \right.$$$

Its Laplace transform is ____________.

Most of the turbidity meters work on the scattering principle. The turbidity value obtained is expressed in

The present population of a community is 28000 with an average water consumption of 4200 $$m^3/d$$. The existing water treatment plant has a design capacity of 6000 $$m^3/d$$. It is expected that the population will increase to 44000 during the next 20 years. The number of years from now when the plant will reach it's design capacity, assuming an arithmetic rate of population growth, will be