A maintenance service facility has Poisson arrival rates, negative exponential service time and operates on a ‘first come first served’ queue discipline. Breakdowns occur on an average of $$3$$ per day with a range of zero to eight. The maintenance crew can service an average of $$6$$ machines per day with a range of zero to seven. The mean waiting time for an item to be serviced would be

In $$PERT$$ analysis a critical activity has

There are two products P and Q with the following characteristics

The economic order quantity (EOQ) of products P and Q will be in the ratio.

A compacting machine shown in the figure below is used to create a desired thrust force by using a rack and pinion arrangement. The input gear is mounted on the motor shaft. The gears have involutes teeth of $$2$$ $$mm$$ module.

If the pressure angle of the rack is $${20^ \circ },$$ the force acting along the line of action between the rack and the gear teeth is