Gating ratio of $$1:2:4$$ is used to design the gating system for magnesium alloy casting. This gating ratio refers to the cross section areas of the various gating elements as given below

$$1.$$ $$Down$$ $$sprue$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ $$2.$$ $$runner$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ $$3.$$ $$Ingates$$
The sequence of the above elements in the ratio $$1:2:4$$ is

The permeability of molding sand was determined using a saturated $$AFS$$ sample by passing $$2000cc$$ of air at a gage pressure of $$10$$ $$g/c{m^2}$$. If the time taken for the air to escape was $$1$$ min, the permeability number is:

Proper gating design in metal casting

$$P:$$ Influences the freezing range of the melt
$$Q:$$ Compensates the loss of fluidity of the melt
$$R:$$ Facilitates top feeding of the melt
$$S:$$ Avoids misrun

The height of the down sprue is $$175$$ $$mm$$ and its $$CS$$ area at the base is $$200\,\,m{m^2}.$$ The $$CS$$ area of the horizontal runner is also $$200$$ $$m{m^2}$$. Assuming no losses, indicate the correct choice for the time (seconds) required to fill a mold cavity of volume $${10^6}\,\,m{m^3}.$$ (use $$g=10$$ $$m/{s^2}$$)